Scots-born Fionna Heiton, who now lives in New Zealand, is keen to off-load the historic Darnick Tower in Melrose so that she can concentrate on running a charity organisation in Nepal.
The Category A listed Darnick Tower dates from 1425 and has been in the hands of the Heiton family since it was constructed.
Ms Heiton expects that Darnick Tower will be especially popular among those with a keen and passionate interest in Scottish history.
The castle has played host to a number of famous figures over the centuries, as Ms Heiton explained to the BBC: “You’ve got a building where a teenage King James V watched from the safety of its battlements while the Scott and Douglas clans fought over his custody in the Battle of Melrose in 1526.
“It’s a place where the iconic Scottish writer Sir Walter Scott, who lived nearby, was a regular visitor and begged John Heiton to sell it to him.”
Among Ms Heiton’s possessions is Darnick Tower’s “Licence to Crenellate”, a document signed by the Earl of Bothwell on behalf of Mary Queen of Scots in 1566, allowing the castle to be adapted and rebuilt.
Charity worker Ms Heiton inherited the property in 2002, but was only able to put it up for sale since last year, when an elderly tenant with a lifelong tenancy agreement was transferred into care.
It is hoped that the castle will be sold for over £695,000. It has had 30 viewers so far.