"It is in response to the Children's Commissioner's report that said significant numbers of young people are at risk of being exploited.
"I think (the risk) has always been there but we have not been as aware of it as we are now."
More top news
The grazing is part of a wildlife scheme to help a flower meadow and the insects that rely on it
A lamp in the tower which houses Big Ben is to be switched off for the first time in more than 70 years.
Sir Bruce entertained audiences for more than seven decades.