Three Mills Island is a wonderful site for anyone interested in historical buildings and materials.  The Building London blog has already covered the magnificent granite paving by the Millhouse, itself full of historical building materials which, along with the associated buildings, will be blogged about on Building London in the future. https://buildinglondon.blog/2022/01/03/27three-mills-granite/
But behind the mill buildings is an area called Three Mills Island or Park and in, or on it, is a fascinating mystery: 3 piles of old stones that no one knows where they are from or how they got there! There are around 30 and they have been cleverly used for a kids playspace called the Wild Kingdom, by ‘We Made That’ and Churchman Thornhill Finch.  
Three Mills Island is not an historic island. The buildings called Three Mills are part of an old industrial site first developed in the 11thC, milling grain, distilling gin and making gunpowder over the millennia. Historically the area north of the mills was called Stratford Marsh or Mill Meads.
Further to the north east of the Three Mills, across the Abbey Creek and Channelsea River was the ancient Stratford Langthorne Abbey, who owned all the land and mills. “Stratford Langthorne Abbey, or the Abbey of St Mary’s, Stratford Langthorne was a Cistercian monastery founded in 1135 at Stratford Langthorne — then Essex but now Stratford in the London Borough of Newham. The Abbey, also known as West Ham Abbey as it lay in that parish, was one of the largest Cistercian abbeys in England, possessing 1,500 acres (6.07 km2) of local land, controlling over 20 manors throughout Essex… The Abbey was self-sufficient for its needs and wealthy besides; some of this wealth came from the ecclesiastic mills grinding wheat for local bakers to supply bread to the City of London… In … 1135, William de Montfichet granted the monks all his lordship of (West) Ham, 11 acres … of meadow, two mills by the causeway of Stratford, his wood of Buckhurst and the tithe of his pannage… [ as well as the Abbey there were ] … workshops for brewing, shearing, weaving and tannery with farm buildings to service the extensive holdings and mills on the Bow Back Rivers. Some of these were tidal mills, like those at Three Mills. These were owned by the Abbey, but the surviving mill was built much later.” 
This abbey was like all others ‘dissolved’ in the 16thC by Henry VIII and it’s stones taken for building. Recent excavations in West Ham have uncovered small parts of the abbey, which Building London will post about. But could some of the stones ended up by the Three Mills?
The meadows then only became an ‘island’ in the 1930s when a new channel was created in the Bow Back Rivers called the Prescott Channel as part of major flood relief work. “The Prescott Channel was built in 1930–35 as part of a flood relief scheme for the River Lee Navigation in the East End of London, England, and was named after Sir William Prescott, the then chairman of the Lee Conservancy Board.”  
It appears from maps that the area has never been built on, and post WW2 aerial photos show only allotments and a monument, to workers who died trying to rescue colleagues in an accident in 1901, topped mound, the monument now replaced by a new one by the river side.
One construction there though was a large embankment for defence against floods, constructed apparently in the 13thC, called ‘Short Wall’ which can be seen on John Roque’s map of 1761, though he calls it the Three Mills Wall. There was also a ‘Long Wall’ on the west side of the Channelsea River.
There are very few references to the Short Wall or Long Wall, let alone their construction and indeed one of the few historic references is only to mention plants being discovered near them in the “Proceedings of the Botanical Society of London, Volume 1, Botanical Society of London, Darton and Clark, Holborn Hill, 1839” 
The one direct reference, where they are called a “sea wall” or “dykes”, is from ‘Houses of Cistercian monks: Abbey of Stratford Langthorne’, in A History of the County of Essex: Volume 2, ed. William Page and J Horace Round (London, 1907)  “The abbot [ of Stratford Langthorne Abbey ] was charged with the repair of the bridges and causeway between Stratford-atte-Bow and Ham Stratford, [ and ] also to a large extent responsible for the maintenance of the sea wall round the marshes of West Ham, and in 1280 … and 1292 … we find him complaining that other persons having land in the neighbourhood refused to make their proper contributions, while in 1339 he endeavoured unsuccessfully to put the whole burden of repairing one of the dykes in West Ham marshes on to the prioress of Stratford-at-Bow.” but there is nothing else about their construction, maintenance over 650 years or destruction in the 20thC.
The walls disappeared at some point after the war, either after the new flood defences of the 1930s were shown to work, or after the major works of the Lee Flood Relief Channel, which started in 1947 and were completed in 1976,  but their names live on as the foot paths. 
So! The mysterious stones!
What are they and where are they from? There are 3 sets. One set seems to be old limestone, weather worn and possibly from a church. One piece has a rose carved into it.
The second set is of granite ‘cheeses’, a couple of them with large metacrysts typical of Cornish or Devonian granites. They appear to be millstones and have had some industrial use. Two of them have a polished rings in it from what looks like wear.
The third set are also granites but have highly polished shaped faces that suggest they may have been part of some sort of pediment.
But no one knows where they are from!
Building London has communicated with people from the House Mill Trust who have restored the Three Mills buildings, Newham Archives, Lea Valley Regional Park Authority and Churchman Hill Finch and We Made That who designed and built the Wild Kingdom play areas that have re-used these stones. And no one knows exactly where they are originally from. It seems certain they were on site in 2010 as it’s said they were in the mounds that were shifted when the current park and ‘hills’ were created but it is unclear how they got into those mounds in the first place! Or where those mounds themselves came from!
There are some clues: the rose, the weather worn limestone, and the circular smooth polished surface on some of the granite ‘cheeses’ suggesting these had some industrial function.
And there were several ideas raised of their built origin:
Euston Arch: Were they some of the stones of the Euston Arch? Some of Euston Arch was indeed found in the Prescott Channel nearby, where they had been used to fill in a scoured hole in the bottom of the river in the 1960s. But the answer is, no, as they do not match the type of stone the Euston Arch was made from, Bramley Fall stone, a type of Millstone. And they also look nothing like the Euston Arch stones.    
Others wondered if they had been part of the Stratford Langthorne Abbey but mostly this seems unlikely. Two of the sets of stones are granites and there would have been no granite in the Abbey. The third set though is limestone and it looks old and worn and so it is possible that these are from the Abbey. Could they have ended up being used as rubble for the Short Wall after the dissolution of the Abbey in the 16thC and then dug up in the 21st century? Someone may be able to recognise and match the rose carving.
This blog wondered whether all the stones could have been part of the ‘’Short Wall’ but the granite would not have been in there. It’s too 19thc. The Short and Long Walls were probably just earth and rubble.
Then there is the monument and it’s mound. Sadly there are no close up pictures of it so it’s unclear if that could have been the source.
And it is possible that the granite ‘cheeses’ are from Three Mills itself. They appear to be milling stones of some design. Not classic horizontal grain grooved ‘scissor action’ millstones but upright crushing stones of some description and certainly with an industrial as opposed to building function, and the Three Mills was not just used for grain milling.
The most likely origin of the other stones is as part of rubble from the clearance of WWII bomb damage from the City and east London. Hackney Marsh is also covered in several meters of this rubble but of course sadly that doesn’t give us any specific origins.
At least 70,000 buildings were destroyed in London so that’s a vast range of options for where these stones are from! [17 
Beverly Charters of the Mill House Trust replied to this last suggestion saying “We’ve always been led to believe that the stones/mounds were WW2 landfill, so Lbth/ city buildings, as you also mention.” [ personal correspondence ] so this does seem the most likely.
However. With the principle that you always miss something with one inspection, a follow up on Easter Saturday 2022 discovered a previously un-noticed and partially hidden stone among the nettles and brambles. And on it is is carved “ .. ARVEY .. YBALL … CHITECT 1908”
It didn’t take long on Google to work out that this was Harvey Dyball a turn of the century London architect. The “Directory of British Architects 1834-1914” tells us that he was born in 1861 with offices at 35 Bucklersbury, London EC, England, commenced independent practice in 1884 and was admitted to the LRIBA in 1910.  Nb the Licentiate membership of RIBA was created in 1905 and was a 2nd class membership.  There are few references to Dyball though one shows he worked on the famous Hare and Hounds pub in Leyton in 1910. 
So what does this new find tell us? It is another indication that at least some of the stones at Three Miles arrived in the 20thC and were then probably part of rubble from bomb damaged London buildings.
Someone at some point might recognise some of the other stones, the rose might be identifiable and the House Mill might look at the granite millstones and see if they could fit into any of the historical processes there, but at this point in history it seems unlikely that any of them will be definitively identified and so the mystery of what buildings these stones are from will remain.
Many thanks for the correspondence and suggestions and ideas to:
Beverley Charters of the House Mill Trust https://housemill.org.uk/
Jess Conway at Newham Archives https://www.newham.gov.uk/libraries-arts-culture/local-history-archives
Ges Hoddinott at LVRPA https://www.visitleevalley.org.uk/
Holly Lewis Co-founding Partner at We Made That https://www.wemadethat.co.uk/
Andrew Thornhill at Churchman Thornhill Finch https://churchmanthornhillfinch.co.uk/
It’s very easy to walk, cycle or get to Three Mills by public transport
By London Underground & DLR – The nearest station is Bromley-by-Bow, which is served by the Hammersmith & City and District lines and is a 10 minute walk away.
The nearest DLR stations are Abbey Road, Bow Church, Devons Road, Pudding Mill Lane and Stratford High Street, and are all a 15 minute walk away
By Bus – Bus routes 108. D8 and 488 stop outside Tesco, Three Mill Lane – a 3-minute walk away and the 25, 276 and 425 stop at Stratford High Street Bow Flyover – a 5-minute walk away
Walking and cycling, Three Mills is on numerous public footpaths along the Lea and Bow Back Rivers.
This is a good guide to the area https://issuu.com/leevalleypark/docs/three-mills
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