A historic stone marking the boundaries between parishes was moved by a council which was unaware of its significance.
Residents and historians were upset when it vanished from Wild Park, Brighton.
Inquiries revealed the stone, which marks the boundary between the parishes of Patcham, Falmer and Stanmer and is marked on Ordnance Survey maps, had been moved by Brighton and Hove City Council to the grounds of a city church in an attempt to stop ball games.
A dog walker noticed council workmen trying to move the stone, thought to have been in the same spot for hundreds of years.
It was too heavy for their truck's grab to pick up but the next morning the stone had gone.
Historian Stuart Mason, of the Brighton-based Antiquarian Society, said: "The man was very upset as he has lived in the area his whole life and remembers playing on that stone 50 or 60 years ago as a child.
"It pre-dates all our living memories and although its exact history is unknown, it could have been in that location for thousands of years."
It turned out the council had moved the stone after being asked for urgent help in curbing football games near St Peter's Church, Brighton, which recently had one of its stained glass windows smashed by a ball.
Mr Mason, 33, of Crayford Road, Brighton, went on: "I cannot believe the council has moved something that is so important to our heritage.
"It is in the centre of a very important historical site.
"It lies between Hollingbury Fort, a neolithic settlement, and a medieval dew pond.
"I am dumbfounded their solution to the problem of football playing is to move a stone.
"It never ceases to amaze me what Brighton and Hove council spends taxpayers' money on.
"I am also dumbfounded they had no knowledge of the significance of the stone.
"You can look on any Ordnance Survey map and there it is, clearly marked with a BS' for boundary stone.
"Other members of the community and I want it put back where it belongs."
A council spokeswoman said: "The church asked for the council's urgent help.
"There were worries that, with World Cup football fever sweeping the nation, games there could mean more church windows being smashed, which would be a huge financial burden.
"We moved the stone to the middle of the grass to make it a less inviting football pitch.
"We weren't aware that this stone was any sort of boundary stone.
"However, if it turns out there is evidence that it was, we'll move it back to its original location."
The Antiquarian Society is a non-profit organisation which offers guided tours around sites of historical interest in Sussex.
For further information, visit www.theantiquariansociety.com
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