Gethin was at West Midlands Police's central prison cells to film a new documentary about how policing has changed over the past 25 years.

A police spokesman said: "Gethin spent the day in our cells. He hasn't been naughty, it's for an exciting new documentary the BBC are making about us.

"We did feel sorry for him. The cells can be quite whiffy on a Monday morning after the weekend."

Gethin was taken to a secret location within the building where the weapons and ammunition are stored after being seized.

A spokesman said: "He loved it, he was like a kid in a candy shop. As part of an exercise which will be featured on the documentary he was asked to pick which guns were real and which were imitation."

"The daytime programme, which is due to be shown in March, looks at how technology has changed policing over the years."

Gethin is the Welsh team captain involved in a Sport Relief Challenge in March 2012. Four teams of celebrated sports people and celebrities representing England, Ireland, Scotland and Wales will race over 1,000 miles around the UK and Ireland. The teams will start simultaneously in their home cities of Cardiff, Dublin, Edinburgh and London and will run, row, cycle and sail their way clockwise around the UK and Ireland from the 10th to the 17th of March 2012. For eight days they will push their bodies to the extreme as they raise a stack of money for Sport Relief.