Historic Michelham Priory has been the target of break-ins on two consecutive nights, say Sussex Police.
Overnight on July 1/2 and 2/3, the Great Barn at the Upper Dicker site was broken into and damage caused to contents.
An attempt was also made to break into the till in The Barn on the second occasion but nothing was taken, police say.
A 27-year-old man from Frant, and a 48-year-old woman from Hailsham have been arrested on suspicion of the burglaries. After being interviewed they have been released on bail until August 17 while enquiries continue.
Anyone with information can contact the police online at www.sussex.police.uk/appealresponse or by calling 101, quoting serial 354 of 02/07.
Michelham Priory dates in part from the 13th century and is the site of a former Augustine Priory. The surviving buildings are owned and administered by the Sussex Archaeological Society and are Grade I and Grade II Listed.