Four ex-SAS bodyguards are protecting Harry Potter star Daniel Radcliffe after receiving a death threat from a stalker.

Worried movie bosses have assigned heartthrob Daniel, 18, the security. He switched cars three times on Saturday night during filming of the sixth movie Harry Potter and the Half-Blood Prince. And his regular driver — used by the star for seven years and considered “part of the family” — has been temporarily stood down.

The nature of the threat, received via Warner Bros, is unclear. But a security source said bosses are treating it seriously and ordered his protection at all times on set and to and from shoots.

The insider added: “There is a real concern for Daniel’s welfare. The bigwigs haven’t said what has been going on. It’s all hush-hush — but security has been massively ramped up.”