Plans to stop developers putting up ugly buildings near Britain's heritage sites have been unveiled.
The 900-year-old Tower of London would be protected by a buffer zone
Britain's 27 World Heritage Sites, including the Tower of London, are not formally protected by planning laws.
But the government is now proposing to put buffer zones around them, in an attempt to prevent the tower being put on a UN blacklist of endangered sites.
In a separate move, Westminster City Council is urging the UN to protect the Palace of Westminster.
Culture Secretary Tessa Jowell wants to change planning laws to give heritage sites similar development protections to those currently given to areas of outstanding natural beauty and national parks.
Britain's World Heritage sites include Durham Cathedral, Stonehenge, Edinburgh's Old and New Towns and Hadrian's Wall.
She said: "Our built heritage and historic environment matter to us all.
"The heritage protection system is about how we protect and sustain it, both for today and for generations to come."
Unesco, the UN's cultural organisation, has already warned that plans for skyscrapers near the Tower of London could put it on its "in danger" list.
It is due to make its ruling in June.
Inclusion on the blacklist would be highly embarrassing for the government. The Tower would be the only world heritage site building in the developed world to be declared "at risk".
Meanwhile Westminster City Council has formally appealed to Unesco to protect the Palace of Westminster and Westminster Abbey, which are part of a World Heritage Site.
The council is concerned that London Mayor Ken Livingstone will use new planning powers to approve plans for more skyscrapers in the vicinity.
At present he can only reject, rather than approve, major developments.
That will change with the introduction of the Greater London Authority Bill 2006, currently making its way through Parliament.
Mr Livingstone will be given complete control over approving as well as refusing "strategic" applications.
The council is particularly concerned about plans for a cluster of buildings around nearby Waterloo Station.