Day 10 of the dig saw us soldier on in the extensions to Trench 2. The circular brick void at the south end of the trench is continuing to cause much head-scratching, not least when it became apparent that there is in fact no properly constructed lid to it - it is covered only by an extremely haphazard collection of mortar and brick and tile rubble.

How on Earth this has survived intact without collapsing for the better part of four centuries is anybody's guess, and how it got there as it is now, is also more than a little puzzling.

Our only plausible interpretation at the moment is that the feature maybe once had a wooden lid which was buried in rubble, and has since decayed away.

We spent much of the morning and afternoon carefully clearing away rubble from the top of the feature, hoping to find a properly constructed roof, but once holes began to open up in the rubble we stopped and recorded the surface of the mortar rich deposit, about the thickness of one brick, which defines the top of the void. (Click here for an annotated version of the above image).

We then dug down on the outside of the feature, on its east side, hoping to be able to expose its external face but the rubble here was so loose that another gap opened up, and so we again paused work to reconsider our strategy.

It's pretty clear now that the covering of the void is not an in-situ structural feature, and so tomorrow we will begin to carefully remove it and finally get a good look at the circle of brickwork inside, and hopefully get a better idea of what it is - it could be a well, or a garderobe chute, a cistern or something else again.

Its function is likely closely related to the adjacent brick 'floor' surface - which today we dug an ever-growing sondage down one face.

To our surprise it has now revealed at least seven courses of brickwork, which means that this is something more than just a floor. Together with the appearance of the well-like void we're now suspecting that the brick surface is perhaps a culverted drain - maybe taking water from the south end of the trench and channeling it north, maybe into a moat.

If this is the case, we can expect the brickwork down the side of the 'floor' to continue down to a considerable depth.

It is also possible, if this is a culvert, that the nearby circular 'well' feature is connected to it, though there's no evidence for that yet.

Meanwhile in Trench 4, the wall that we've been working hard to reveal all week finally appeared. This trench was placed on the location of a wall junction we only saw part of late on in last year's dig, and was intended to confirm whether the wall was a corner or a junction.

We can now confirm it is a junction, and a spur of the wall continues south-west, which means our gatehouse is larger than we previously thought. It is a very substantial wall, as you might expect for the foundations of a four-storey building.

We also continued to excavate Trench 4, in which we have abandoned hope of finding signs of the 1960s trenches, but in recompense it is producing one or two nice finds including another large chunk of the brilliant blue Westerwald jug we found part of on day 8.

We returned from a hard-earned day off, back to the woods of Forty Hall today, and our diggers' hard work has begun to reveal some increasingly interesting, and typical for for the site of Elsyng Palace, enigmatic features.

We ended day 8 in Trench 2 having revealed an asymmetric brick surface, partially laid obliquely over a wall at its north end, and perpendicular to the foundations of another at its south end (the two walls likely meeting to form a corner in a trench we dug last year). This was further complicated by a deliberately filled slot at the floor's north end, and possibly another at its south end. See day 7 for pictures.

We started the day today by removing non-structural rubble from around the southern wall, and it now looks like the southern of the two slots through the floor was an illusion, and the floor in fact abuts the south wall.

However, removing rubble in the south-east corner of the trench revealed a surprise - a hole has opened up into a sizeable void beyond the south end of the trench.

It's just about big enough to get a camera into, and as far as we can see it is lined with a curved brick face to a depth of at least 9 or maybe 10 courses - a depth of about 60cm.

The roof of the chamber is either loose rubble or very haphazardly mortared brick fragments - it is possible that there's a better-built roof to it above.

We have therefore opened a 2x1m extension over the top of it and have removed topsoil and most of the ubiquitous pebble context that covers the whole area. We've just begun to reveal the rubble layer that likely lays on top of whatever this feature is, and will have to devise a careful excavation strategy tomorrow to avoid loosing one of our diggers into the chamber headfirst!

Meanwhile at the other end of the trench we opened a similar extension, aiming to reveal more of the other wall and hopefully the north end of the brick floor - due to their oblique angles relative to one another the edge of the floor and wall should come together somehow somewhere not far away.

We again got as far as the beginning of the rubble deposit, although some of it looks as if it is in-situ, possibly meaning that the structures are not demolished as deep at the north end of the trench.

The most interesting find of the day was a chunk of yellow-glazed floor tile from Trench 3 which is still being dug down to the level of the expected wall junction.

We have seen plenty of glazed floor tiles before but never one with graffiti scratched onto it. This one has a series of overlapping circles scratched onto its reverse side.

Circle-based geometric designs are a common form of graffiti, and are often found in buildings (especially churches) in England, from the early medieval period up until the 19th century.

Sometimes known as "witches marks", their meaning or purpose, if any, is disputed - see https://historicengland.org.uk/whats-new/features/discovering-witches-marks/what-are-witches-marks/ for more information.

Whether a secret symbol deliberately placed beneath a floor to ward off evil, or a bored apprentice with a pair of dividers, it's a nice human touch we very rarely see on ordinary building materials.

No significant developments to report on day 8 of our two week dig on the site of Elsyng Palace.

We spent most of the day making detailed plans, surveying and photographing the brickwork in Trench 2.

We're still not sure what the purpose of the brick floor is in T2, nor the two apparent channels at either end of it. We don't think it's likely that they are drains, since they don't seem to lead to or from anywhere, so the balance of evidence at the moment points to slots for timber beams.

Having studied the mortar of the walls at either end of the trench (see the diagram from yesterday) we think they date to the early 16th century phase of the palace, when it was remodelled by Sir Thomas Lovell.

Since the floor is laid on top, it must post-date that phase and so may be part of the work done in the early 17th century, when the palace was again remodelled and reduced in size by James I, before it was given as a grace-and-favour home to his friend the Earl of Pembroke.

This is all still very speculative, and in order to understand it better we want to see more of the structure, particularly at the north end of the trench.

As often happens we've unfortunately placed a spoil heap slightly too close to the trench to extend in that direction so we bit the bullet and spent part of the afternoon moving it out of the way.

We still have two other trenches open - T3 which will eventually come down onto the wall junction we saw last year (see Day 1), and T4 over at the western end of the site, in search of the 1960s trenches.

Work in both these trenches has become hard-going as they've had a long time to bake in the hot and dry conditions.

Trench 4 has almost certainly not hit any 1960s backfill, but there is a deposit of very compacted brick rubble in one corner and it has begun to produce some small finds, including a few very striking fragments of "Westerwald" stoneware - probably a jug - decorated with a brilliant cobalt blue glaze.

Westerwald pottery comes very late in the chronology of Elsyng - in this case most likely dating to the mid-17th century - and so this vessel would have been amongst the last high quality tablewares imported onto the site before its final demolition circa 1660.

This and a few other finds in Trench 4 further point to its never having been dug before. We will fully excavate this trench but it looks probable now that we won't have time this year to open any more trenches targeting the 60s work.

Monday is our day off, but we'll be back on Tuesday to wrestle the remaining secrets from our open trenches.

A busy day today as we come to the end of the first week of our two-week dig in Forty Hall on the site of Elsyng Palace.

Today was our public open day, and we were pleased to welcome a steady stream of visitors all day, who joined us in scratching their heads at the impressive but somewhat enigmatic medieval/Tudor brickwork that was emerging from Trench 2.

Once we'd set up our displays and stalls, we finished exposing the brick floor in Trench 2, fully defining the edge of the wall that runs partly beneath it on its east side.

We also removed the rubble at the south end of the trench, which as expected revealed another wall under it. During this process it began to look as if there is another channel cut through the floor, although this one seems to have rubble in it rather than tiles like the other one - see the image to the right, and click here for an annotated version.

So, in this trench we currently have a brick floor surface, bounded on the south side by a wall, and with two parallel slots through it, with a second wall running partly beneath its east edge.

Since the floor is partially laid on top of it, the wall must pre-date the floor. The wall may therefore belong to the early 15th century phase of the palace as built by the Earl of Worcester, with the floor representing the extensive improvements made by Sir Thomas Lovell after his acquisition of the palace circa 1497.

Exactly what the floor and the channels are for is not yet clear. All this brickwork is along the back edge of the gatehouse, so we might expect the threshold to a rear entrance. In this case, the parallel channels may be the remains of beam slots that once supported a timber frame for something like a porch.

This theory was slightly confounded very late in the day, as we began to remove the jumble of roof tiles from the northern channel, only to find more tiles beneath, tightly mortared together. This begins to look as if the channel has been hastily and crudely blocked up - which you might expect of a drainage channel that went out of use.

There's still plenty more work to do on all of this to make things clearer, and a whole week to do it, including the continuing search for evidence of the 1960s trenches. Work continued in Trench 4 to that end today, and it is beginning to look unlikely that it contains 1960s backfill.

A day of excitement in Forty Hall today, but sadly for the wrong reasons.

A large grass fire broke out this afternoon on the east side of the lime tree avenue and rapidly spread, alarmingly initially towards the dig site.

A fortunate change in wind direction eventually carried the fire away to the east towards Maidens Bridge, before the London Fire Brigade arrived and were able to get it under control before it spread to any major groups of trees.

The first fire engine arrived very quickly and we were able to assist it onto the site, where its crew did an excellent job dousing the main flames, but a second engine was delayed by another call en-route, so EAS members lent a hand beating out and dousing smoldering hotspots with buckets of water from Maidens Brook, while the fire crew handled the main flame front.

Once the second engine arrived everything was quickly put out and the crews spent most of the rest of the day damping down the scene.

Meanwhile, back at the archaeological dig:

Just before all the excitement, we had just opened our fourth trench, about ten metres to the west of Trench 1, in another attempt to identify the complex of trenches first dug by the EAS in 1963-66.

This is as far west as we can go this year, and on the face of the available evidence we don't think the 60s work can have been significantly further west than this. If this trench draws a blank as Trench 1 did, we have a couple more options nearby, but our chances of finding the 60s work this year would start to seem really very slim, and we would need to seriously re-appraise our evidence for where the 60 work took place.

Things were much more optimistic in Trench 2, however, which is now rapidly producing a rich assortment of brickwork.

The rough brick surface we began to reveal yesterday is now almost entirely revealed, with a distinct edge along its west side. Where it enters the east section of the trench there is a rough tumble of bricks which may or may not be concealing a wall beneath. Just before it enters the west section (foreground of above image) there is a stack of tiles which look to be filling a slot through the surface. We can't tell yet if this is deliberate, for example a collapsed drain, or a coincidental tumble.

Along the east side of the brick surface (upper left in above image) there seems to be the remains of a wall, running on a different alignment to the surface, and we think beneath it (i.e. the brick surface is later and built on top).

There is a lot of work to do to make sense of all this and a lot of careful unpicking of rubble still to go, but the next major job in this trench will be planning and photography tomorrow morning, that is after we've set up all the gear for our public open day.

Let's hope it's not as much of a scorcher as today.