The brother of a Jewish businessman strangled during a robbery has vowed to help catch the killers while police say a rare Cartier watch may lead to key clues.

John Luper, 57, was killed while his wife and daughter were tied up at their home in Alwoodley, Leeds, in 2004. Jewellery worth £100,000 was taken and police say local criminals know the culprits because the incident became notorious in gangland circles.

On the 10th anniversary of the killing, John’s brother Toby pledged to help catch those responsible “while I’ve still got breath in my body.”

“It’s still raw. I was angry at the time, but now I’m not angry, I’m more determined than ever.”

West Yorkshire police say a rare platinum Cartier watch stolen from Mr Luper is a key clue and have appealed to anyone who may have seen it.

Det Ch Insp Simon Atkinson said his investigation “will never end”.