A burglar who hid in the roof of south London supermarkets to intercept cash deliveries has been jailed for five years.

Peter Blackham, 26, a former supermarket employee from Petts Wood, pleaded guilty to 10 charges of commercial burglary worth more than £90,000.

Croydon Crown Court was told Blackham had climbed into the roof of supermarkets in Purley Way and New Malden as well as others in London and Kent and intercepted cash as it flew through vacuum tubes connecting the shop tills with their secure cash storage rooms.

The court heard Blackham had locked himself in disabled toilets before removing ceiling tiles to get in to the roof of at least one supermarket.

Prosecutor John Gardner said staff at the Purley Way branch of Sainsbury's began to notice large amounts of cash going missing on a regular basis last March.

"They brought in investigators and, at first, their objective were the till cashiers, and then the department itself," Mr Gardner said.

"This proved fruitless, so they started looking at the way the cash was taken from the tills to the department."

Money was still disappearing until, eventually, Blackham was seen in a restricted area with £314 in his pocket.

He was arrested, but denied having been in the roof. At his home in Kent, police found £1,000.

Mr Gardner said: "He was bailed and then, in February this year, Tesco at Sidcup started to notice that cash was being lost and they did their own investigation. The store used the same vacuum flight system as that of Sainsbury's."

Police traced two vehicles parked at the supermarkets at the time of the thefts back to Blackham, who had hired them at £250 a week.

Meanwhile, police came across a small spot of blood on a roof tile at the Hatfield branch of Sainsbury which was matched with Blackham.

Officers again went to his home and asked him if he had taken anything from Tesco. He replied "Yes" and produced £4,605 from his trousers pocket.

"Also found was a small wrap of what was believed to be cocaine," Mr Gardner said.

Police discovered documents showing Blackham was in considerable debt.

Blackham pleaded guilty to nine burglaries and asked for a further 10 to be taken into consideration.

Judge Warwick McKinnon told Blackham: "These offences were highly sophisticated and a carefully-planned series of burglaries with some detailed knowledge of the working of the supermarkets and the way they deal with cash."

Judge McKinnon said it was a tragedy that a man of Blackham's education and promise had turned to crime.

"You were bailed and carried on doing exactly the same thing at Tesco which used precisely the same system."

The judge added that Blackham's cocaine addiction might have been partly responsible for the thefts.