The widow of a Nobel Prize winner believes two break-ins at her home may have been carried out by thieves looking for his gold medal.

Lady Rona Black, whose late husband Sir James Black invented beta blockers, said her London home was burgled on December 29 and again on Wednesday.

She believes the men who targeted her may have been looking for the Lanarkshire-born scientist's 1988 Nobel Prize for Medicine medal and his Order of Merit insignia.

Lady Black, who is also a distinguished medical scientist known professionally as Rona Mackie, said neither medal is actually kept at her home.

The 77-year-old said: "They do seem interested in medals and I just wonder if it is that.

"My husband's Nobel medal and all his other important medals we donated to the National Museum of Scotland a decade ago, so there is nothing like that in this house.

"The other lovely honour he got was that he was a member of the Order of Merit. The Order of Merit is a beautiful bit of important jewellery.

"That was handed back to the Queen, that's the pattern when the holder dies, the next of kin hands it back. These things are not in this house."

Sir James died in March 2010 at the age of 85.

His invention of the beta blocker drug propranolol is considered one of the major breakthroughs in pharmacology of the 20th Century and ultimately led to the lives of hundreds of thousands of heart patients being saved.

He also made significant discoveries in the development of drugs to treat heartburn and ulcers.

He won the Nobel Prize for medicine for his work on drug development in 1988.

Lady Black said she discovered the first burglary in her bedroom after arriving home from spending Christmas with her family.

They got away with Sir James's 1981 knighthood insignia, two or three of her own medals and most of her jewellery after breaking into a safe they had tried to drill out of a wall.

She said that after that first crime she upgraded security, including installing CCTV and better lighting outside.

But on February 14 she was 200 yards away visiting friends when her neighbour called her to say her alarm was going off again.

This time they got away with her remaining jewellery and her passport after gaining entry to the rest of the house.

Lady Black said it had been a "a very unpleasant week", adding: "I was a bit shaken this time because I really did think I'd made myself pretty safe.

"Basically the police's view is that this was a return visit of a team - I gather in my part of south London there is a lot of burglary just now - they think it's a return visit of someone who didn't get what they wanted the first time around."

She added: "The only reason I am looking for publicity is to send out the message that there are no valuable medals in this house at all, and there is now no jewellery in this house so don't bother coming back - there is nothing worth selling."