The gunman who shot Miss Dando on her doorstep in Fulham, west London, in April may have left his personal trademark on the fatal bullet.

Six distinctive marks were found on the cartridge case which have never been seen either in the UK or elsewhere, said Det Ch Insp Hamish Campbell.

The BBC's Graham McLaggen reports

Forensic experts in the UK, Europe and further afield have all inspected the tiny marks, made with hammer blows, but none recognised the symbols.

The marks would have had the effect of holding the bullet in place by "crimping" the cartridge case, but the firing of the bullet would not have been affected, Mr Campbell said.

He said the markings could have been a trademark, habit or idiosyncrasy.

Mr Campbell appealed to gun dealers and anyone handling ammunition to get in touch if the markings meant anything to them.