St Paul\'s Cathedral is to close to visitors for the first time since World War II because of the anti-capitalist demonstrators camping on its doorstep, its dean has said. The decision was taken with a \"heavy heart\" for health and safety reasons, said the Right Reverend Graeme Knowles. The Occupy London Stock Exchange movement has been located close to Paternoster Square since Saturday. The dean has asked the activists to move on from the area by the entrance. olice presence \"We have a legal obligation to keep visitors safe and healthy,\" he said. The cathedral will close to members of the public after a service on Friday afternoon. On Sunday the cathedral\'s canon chancellor, the Reverend Giles Fraser, said he had asked for the police presence outside the building to be scaled back. By Wednesday, the higher number of protesters meant officials had to review \"the extent to which it can remain open for the many thousands coming this week as worshippers, visitors and in school parties\". Speaking outside the cathedral on Friday, Dean Knowles said: \"I have written an open letter to the protesters this afternoon, advising them that we have no lawful alternative but to close St Paul\'s Cathedral until further notice. \"The health, safety and fire officers have pointed out that access to and from the cathedral is seriously limited. \"With so many stoves and fires and lots of different types of fuel around, there is a clear fire hazard. \"Then there is the public health aspect, which speaks for itself. \"The dangers relate not just to cathedral staff and visitors but are a potential hazard to those encamped.\" Last year the cathedral earned an average of £22,600 a day from commercial activities, which included income from 820,000 paying visitors