A commercial diver has been jailed for two years after removing three cannon from a 17th Century shipwreck and fraudulently selling them for £46,000.
Vincent Woolsgrove, 48, from Ramsgate in Kent, admitted fraud in July after originally claiming the weapons were found in international waters.
He later admitted he had recovered them from the wreck of The London which sank off Southend in Essex in 1665.
He has also been ordered to pay £35,000 costs at Southampton Crown Court.
In 2007, Woolsgrove found five cannon at the wreck site but claimed only two had come from there, which as they were in UK waters were the property of the Crown.
He insisted the other three cannon were from international waters off the Kent coast and, after he was granted title for them by the Maritime and Coastguard Agency (MCA), sold them to a private collector in the USA in 2010.
A subsequent investigation involving Historic England, the MCA and Essex and Kent police, was able to prove the cannon, which originally came from Dutch ships, were also recovered from the wreck of The London.
Mark Harrison, Historic England's crime advisor, said: "This case sets an important precedent in the fight against uncontrolled salvage by a small criminal minority who have no appreciation for England's maritime heritage.
"Woolsgrove used sophisticated techniques and equipment to remove these valuable artefacts from the seabed."
Essex Police said had he declared the find "he would have been in line for a substantial salvage reward".
The MCA is working with US authorities to arrange for them to be returned to the UK and it would be seeking to get a Proceeds of Crime Act confiscation order against Woolsgrove later.
In a separate official operation, a gun carriage was raised from the wreck of The London in August.