Police are urging the public to use different codes at gyms after a prolific thief stole hundreds of pounds from a man when he entered his locker code - which was also used for bank cards.

Declan Murphy, 35, secretly watched his victim enter the combination to his locker at a luxury gym in central London last September. After stealing the victim's cell phone and bank card from the locker, Murphy then successfully guessed that the four-digit PIN on the card would be the same as the locker combination.

He stole £500 from the account and damaged his own time by dousing the victim's phone in water and blocking access to his banking app.

Isleworth Crown Court heard Murphy, from Bromley, was caught using fake membership cards to enter Third Space and Nuffield Health gyms on multiple occasions.

He also withdrew £1,750 using three different bank cards stolen from different gyms and attempted to withdraw £600 using another stolen card.

The court heard the victim who lost money was eventually compensated by the bank.

Murphy was jailed for two years and three months on Friday after pleading guilty to three counts of theft and 11 counts of fraud by false representation. Sentencing Judge Edward Connell described Murphy's offending as "pre-planned" and "carefully practiced".

Police said the technique has been used by other criminals and warned the public to always use different codes on lockers and bank cards.

DCI Kevin Ives, of Metropolitan Police, said: “Gym-goers expect their belongings to be stored safely in lockers and don’t expect someone to spy on them and steal their passwords.

“Unfortunately, we know this is the method used by prolific criminals like Murphy.

"Our message is clear, do not use the same PIN for your locker as your phone or bank card PIN."

London police said Murphy targeted a luxury fitness club called Third Space in London. After the theft, the victim, who had joined the gym after his wife died of cancer, discovered Murphy had called the bank pretending to be him and accessed the bank account over the Internet.

The victim noticed a missed call from the bank but had difficulty returning the call because the phone was damaged by water.

Murphy withdrew £500 from the cash machine and later that day he tried unsuccessfully to buy £5,400 worth of goods from an Apple store. The sentencing hearing heard Murphy owed a debt of £15,000 and stole the cards in an attempt to repay the debt.

The victim told the court how the thefts had increased his "sense of isolation" following the death of his wife.

Murphy was also handed a criminal behavior order banning him from visiting any Third Space or Nuffield Health gyms for six years.