Archaeologists claim to have found the remains of a chapel built by Richard III after a 16-year search.
The chapel, to commemorate the Battle of Towton (1461), was begun by Richard in 1483 but his death two years later meant it was never completed.
A team from the University of York said masonry found at Towton, Tadcaster, North Yorkshire, was "likely" to be the remains of the structure.
The team said a larger excavation would be needed to prove it beyond doubt.
Lead archaeologist, Tim Sutherland, has been searching for the remains of the chapel since 1997.
"We were beginning to think there was no structural remains left but we eventually came across large chunks of medieval masonry.
"We've talked to various stonemason experts and they have said 'yes it is almost certainly evidence of a late 15th century ecclesiastical structure.'"
The Battle of Towton was a key battle in the Wars of the Roses, a dynastic clash for the English throne in the 15th century between the Houses of York and Lancaster.
Historians regard it as one of the bloodiest battle on British soil with up to 28,000 men being killed.
The Yorkist victory at Towton ensured Edward of York became King as Edward IV replacing the Lancastrian Henry VI.
Edward IV died in 1483 and his brother Richard III took the throne.
Work began on the chapel but, Mr Sutherland said, it is not known how complete it was when Richard was defeated and killed at the Battle of Bosworth in 1485.
He said the chapel's exact location was not being disclosed as it was on private land and excavation work was continuing.