Lord Avebury says he is pleased that Silbury Hill in Wiltshire is to be protected from walkers.
Silbury Hill dates back to the Neolithic period
The Countryside Agency wanted to classify Silbury Hill in Avebury as "unimproved chalk grassland", which would have opened up some access.
Lord Avebury, who owns the freehold on the land, said walkers were damaging the historic site.
"The important thing to remember when people go to the site is it's a very delicate area," he said.
"New signs will be put up by English Heritage, and a new fence will be erected to stop people trespassing.
"There are people who ignore the notices not to walk there, and up until recently the fence was so damaged people just climbed all over it."
Ramblers, who have not been allowed on the hill since 1974, welcomed the decision.
Ron Moore, area chairman of Wiltshire and Swindon Ramblers' Association, told BBC News: "It is an important historical monument and we weren't much in favour of opening it up."