Even now, Tom Watson routinely memorises the number plates of unfamiliar cars outside his house.

''To be targeted like I was - to be followed by covert surveillance specialists, to have someone try to destroy your character - is very threatening,'' says the British Labour MP who helped blow the whistle on News of the World's phone hacking scheme.

Fears for democracy: British Labour MP Tom Watson. Credit:Ken Irwin

In 2011, it was revealed Mr Watson had been stalked by the paper's private investigators as payback for his dogged investigation of its affairs. News International's executive chairman James Murdoch apologised ''unreservedly''.