A huge 19th Century anchor is due to go on display at Chatham Dockyard, after being discovered in the River Thames off Kent.
The origins of the anchor, which is over 15ft (4.5m) tall and weighs more than five tonnes, are a mystery, the Port of London Authority (PLA) have said.
It was removed from the Thames close to Northfleet after a survey of the river bed identified it as a risk to navigation, the PLA said.
Jim Denby, from the PLA, said: “There is no record of how this could have come to be in the riverbed and no report of any vessels losing it.”
We were surprised by the size of the anchor
The anchor is now in a treatment bath to prevent it drying out and the surface cracking, the PLA said.
Karoline Sofie Hennum, conservator for Chatham Historic Dockyard trust, said “As the anchor has been resting on the seabed for quite some time, it has started rusting. We estimate the conservation process could take up to two years to complete due to the anchor’s size.”
Work is underway to try and identify the origin of the anchor and how it came to rest in the Thames.