LONDON, Aug 19, 2009 (AFP) - London police have arrested two men in connection with what is thought to be Britain's biggest jewellery heist, a spokesman said late Wednesday 19 August.

A combination of handout pictures from Britain's Metropolitan Police shows some of the 43 jewellery items stolen from Graff's jewellery store in London. London police have arrested a man in their hunt for the smartly-dressed robbers who pulled off what is thought to be the country's biggest jewellery heist - Photo: AFP/HO

Two gun-toting and smartly dressed men walked into an exclusive Graff store in central London and stole 43 rings, bracelets, necklaces and watches with a retail value of 40 million pounds (47 million euros, 65 million dollars).

The Metropolitan Police said the pair were arrested Wednesday 19 August but would not issue any more details for "operational reasons" -- including whether they were the same two captured on video pulling off the raid earlier this month.

A record reward of up to one million pounds has been offered to find those behind the robbery in broad daylight on London's swanky New Bond Street.

A 50-year-old man has already been arrested over the robbery, which police have said was well organised and could have involved accomplices.

The two men, dressed in grey suits and white shirts and speaking with London accents, arrived in a black taxi and threatened staff with handguns.

As they left, they dragged a female staff member with them and fired a warning shot outside. They left her behind as they raced off in a blue BMW.

They abandoned their car nearby, firing another shot at the ground. No one was hurt.

Graff, which is known for its diamonds and caters to celebrities, was also targeted in 2003 in what until now was reportedly Britain's previous most expensive jewellery robbery, worth 23 million pounds.

Stars spotted wearing Graff's jewels include Paris Hilton, Kylie Minogue, Naomi Campbell, Oprah Winfrey and Victoria Beckham.

The latest heist is also thought to be the second biggest robbery in Britain, after a 53-million-pound raid on a Securitas depot in Kent, southeast England, in 2006, police said. A gang tied up staff and stole cash.