Crime author Patricia Cornwell has taken out full-page ads in two national newspapers to deny she is obsessed with Jack the Ripper.

Cornwell claimed artist Walter Sickert was Jack the Ripper in a book in 2002. Ripper experts rejected that theory.

In Saturday's Guardian and Independent, Cornwell stands by her claim and calls on others to disprove it.

The ads are thought to have cost more than £10,000 each. An updated edition of her book will appear next year.

Cornwell wrote in the advert: "My ongoing investigation is far from an obsession but an excellent opportunity to provide a platform for applying modern science to a very old, highly visible case."