The theft happened on Northampton's Racecourse during a game between the Northampton Heathens and the Northampton Old Scouts' third team.

Old Scouts were short of players and were grateful when a member of the public offered his services.

The players thought it was just bad luck when their new teammate hobbled off with an injury early in the second half.

However, their sympathy turned to anger when it became clear that the seemingly helpful player had used the opportunity to rifle through their bags and coats.

Wallets, cards, cash, mobile phones and jewellery – including wedding rings – were stolen.

Keith Shurville, the president of Northampton Old Scouts, said: "He said he was injured and asked if he could get his belongings from his own stuff.

"Everyone was concentrating on the game. By the time they realised what had happened, this guy was gone.

"My feelings about what he did are not printable."

Saturday afternoon's match was abandoned six minutes into the second half, with Heathens leading 7-5, as the angry players called the police.

The raid was not the first time Old Scouts had fallen victim to thefts during a game.

Three years ago, changing rooms were broken into during a match and belongings were taken. Police later arrested the thief.

Players said the conman on Saturday had been wearing a rugby top when he volunteered to play.

Mr Shurville warned other teams to be on the lookout for more attempted cons in similar circumstances.

Northamptonshire Police said the theft happened at about 3pm and up to 16 players had valuables taken.

They say the man may have piled all the stolen items together before carrying them off in a gym bag.

Anyone with information about the thefts can call police on 08453 700 700 or Crimestoppers on 0800 555 111.