June Richardson, whose four-year-old son Martin Brown was murdered by Bell when she was 11, added her voice to the condemnation of an author's decision to pay the convicted killer.

Outrage greeted Gitta Sereny's second book-length study of the controversial case as soon as it became clear she had passed on part of her advance for the book to Bell.

June Richardson: protesting

Ms Sereny said she had spent months interviewing Bell for Cries Unheard and believed that she would have exploited her if she had not offered payment.

The Home Secretary Jack Straw and the Prime Minister Tony Blair were among those who appeared to disagree.

Although the payment of convicted criminals by newspapers is against the code set out by the Press Complaints Commission, the government realised there was little it could do to counteract the deal struck between Ms Sereny and Bell.

It promised to amend the law so that such a situation could never arise again.

Martin Brown: murdered

The protest in London brought together victims' families from some of Britain's most notorious crimes.

Mrs Richardson, who has travelled from her home in Tyneside to take part, joined Winnie Johnson, whose son Keith Bennett was one of the victims of Moors Murderers Myra Hindley and Ian Brady.