Jewellery Marilyn Monroe wore on her first date with baseball star is stolen from exhibition

Jewellery worn by Marilyn Monroe at the height of her fame in the 1950s has been stolen from a London gallery.

One man smashed a display case and grabbed a diamond-encrusted gold ring and a gold bangle worth an estimated £40,000 while the second diverted a security guard.

The men fled the gallery at County Hall on the South Bank and tried to disappear in the crowds around the London Eye. The gallery's head of security caught a man after chasing him along the South Bank. A 45-year-old man was released on bail yesterday.

The ring, which has an "M" motif, and the bangle, which Monroe is believed to have worn on her first date with the baseball star Joe DiMaggio, were lent to the gallery by a private collector. The man, who has not been named, is said to be devastated.

The items were among more than 250 items on show at the exhibition Marilyn Monroe – Life of a Legend, which opened last week. Described as "the biggest ever exhibition devoted to the life of the ultimate screen icon" it is due to spend three years travelling the world.

Monroe gave the jewellery to Bebe Goddard, a childhood friend with whom she lived after leaving a series of orphanages. Since then, the items have passed through several owners on the lucrative circuit in celebrity collectables.

The gallery, which was open again yesterday after the break-in on Monday afternoon, has beefed up its security.

The thieves barged in without buying tickets and are believed to have knocked over the display case. It contained six items of jewellery worth a total of nearly £200,000. Guards and some of the 150 visitors stopped the thieves taking other items. Detective Inspector Tim Forber appealed for help from anyone who may have been offered the jewellery for sale or who was at the exhibition at the time.

Antonia Spanos, the gallery's head of exhibitions, said: "Marilyn wore these items of jewellery when she was going out but she had so much stuff, she would give things away to people who were like her surrogate family." She said some of the other items in the exhibition were more valuable than the jewellery and that the thieves had not been experts.

The jewellery had been held by the auction house Cooper Owen on behalf of the owner. "We were assured there would be security guards and they would be held in a secure casing. The owner is absolutely devastated," Ted Owen, the managing director, said.

Among the items on show are previously unseen photographs, mementoes and designer dresses. Works by Andy Warhol, Peter Blake and Henri Cartier-Bresson, inspired by Monroe, are also on display. Monroe died in 1962, aged 36, from a drug overdose. She was at the peak of her career.