The National Trust has removed a large British flag that was put up at Penshaw Monument without permission.
The charity said the union jack had been attached to the Grade I listed building, near Sunderland, overnight.
An assessment will also be carried out on the 70ft (21m) tall monument, which was built in 1844 in memory of the 1st Earl of Durham, to make sure it was not damaged.
Thousands of British and St George’s flags have appeared across England in recent months, including on the Angel of the North in Gateshead.
A National Trust spokesperson said anything that was attached to historic buildings “without permission” would be removed.
“We will assess whether any damage has been caused to the monument, which is an important part of our shared local and national heritage,” they said.
The Penshaw Monument, more formally known as the Earl of Durham’s Monument, is a replica of a Greek temple and is a prominent landmark in the north-east of England.
It was finished in 1845 and was built to commemorate John Lambton, 1st Earl of Durham.
The National Trust has owned Penshaw Monument since 1939.
Visitors can access the view from the top via a spiral staircase inside one of the columns on official tours at certain times of the year.
