A chauffeur who blackmailed the Qatar royal family for £600,000 after finding private photos on equipment left in the back of his car has been jailed for four-and-a-half years.

Sudan-born Awad Abdulbagy, 49, threatened to sell the 350 pictures to a commercial television station or one of the Gulf state's rivals, including Syria, after they were left on a camera and memory sticks during a royal visit to London in May 2013.

But the Qatari embassy staff, instead of paying him and his wife Nasren Mohammed the "life-changing" sum they wanted, called police and he was arrested over the "amateurish" scheme, London's Southwark Crown Court heard.

Sentencing Abdulbagy and Mohammed, 34, Judge Anthony Pitt said that, while the pictures had included "nothing disgraceful", they had been private and were "highly sensitive" given who they belonged to.

The judge accepted that at first the couple had considered just handing the pictures and equipment back honestly, perhaps in return for a small thank you payment.

He told Abdulbagy: "I don't know what they would have paid ... but shortly after you turned to criminal threats as to how not just to get a small thank-you, but how to get a life-changing amount of money.

"It was an opportunity that formed in your mind, and perhaps that of your wife as well, of gaining a large sum of money, a life-changing sum of money. A ransom, in effect, for the return of the items."

He added: "These were private pictures of the royal family, with the added sensitivity of pictures that were not meant to be broadcast to the good people of Qatar."

The court heard that Abdulbagy had been hired in late May 2013 to drive the Qataris' private photographer and baggage around London and to and from Stansted Airport after they arrived for a visit in a private jet.

After one trip he found several items left in the back of the car, containing the images. The couple then approached the Qatari embassy in Mayfair, initially asking for £600,000 before reducing their demand to £300,000 for returning the equipment containing the images, the court heard.

The couple, who have five children aged three to 11, two of whom are disabled, wept in the dock as they were sentenced for their roles in the blackmail.

Abdulbagy, who the court heard had previously worked as a chauffeur for several rich Arab customers, came to the UK from Sudan in 1997, the court heard.

Mohammed, who claimed asylum here in the mid 1990 from Sudan, where her father was a politician, was given a two-year jail sentence suspended for two years.

Judge Pitt said her sentence was suspended as an "act of mercy" to the couple's children. He accepted she had a "lesser role" in the plot but said he suspected the intelligent, well-educated Middlesex University IT graduate turned full-time mother had been the "steel in the back" of her husband.

The court heard she had been the one to first telephone the embassy, saying they "wanted to collect a prize". It also heard that with her husband in prison she will be left caring for the children on benefits.

The couple, of Shepherds Bush, west London, were found guilty of one count of blackmail at a trial earlier this year. A third defendant, Khaled Wattar, of Acton, west London, was cleared of blackmail by the jury.

A charge of theft against Abdulbagy and a charge of handling stolen goods against Mohammed will lie on file.