Princess Anne will attend the Minden Day parade in Berwick to help mark a special date in the history of the King’s Own Scottish Borderers.
The parade commemorates the King’s Own Scottish Borderers’ participation - and most famous victory - in the Battle of Minden in 1759.
It is usually held on the Saturday closest to August 1 but has been moved to Thursday, August 1 this year to accommodate its royal visitor.
It also coincides with the 250th anniversary of the KOSB being based in Berwick Barracks.
Princess Anne will meet officers and former soldiers in the barracks from around 10.30am where she will hand out Minden roses.
She will then oversee the laying up of the colours in the KOSB regimental museum, the culmination of a long campaign.
Ed Swales, regimental secretary, said: “It will be a very proud moment to have the colours coming back to Berwick to be laid to rest.”
Princess Anne will then watch the parade down Marygate at around 12.15pm. Around 650 ex-soldiers are expected to take part - close to three times what there would normally be.
However, the numbers mean it will not be possible for them to congregate in the barracks square beforehand. Mr Swales said: “We’re limited to 250 in the barracks square and the tickets have all gone. We want as many people as possible to come along and watch the parade but the best place to do so will be on Marygate.”