A police station and the surrounding streets were evacuated when a man walked in and placed a bomb on the front desk.

Martin Welsh stunned officers when he walked in carrying a heavily corroded German hand grenade and placed it on the counter.

The 57-year-old, who runs a house clearance business, discovered the device under the stairs of a house that belonged to an elderly woman who died after living there 60 years.

Wrongly believing it had been deactivated, he drove it to the police station but, finding it closed, took it back to his home near Chichester and left it in his garden shed.

It was another week before he returned to the city's police station yesterday, prompting an emergency evacuation.

The station and roads surrounding it were sealed off and bomb disposal experts called in after Mr Welsh's delivery at 11am yesterday.

Experts identified the item as a First World War German egg bomb - a type of grenade - and took it to a field at the rear of the station.

They waited until children at a nearby school had left after breaking up for the summer holidays, then carried out a controlled explosion at 1.20pm.

Meanwhile, a shocked Mr Welsh was full of apologies as police warned he had risked his life in moving the grenade from the house in Old Bosham.

He said: "I was told by a neighbour it was a deactivated grenade. I had a skip and I could have put it in there but I thought I'd take it to the police station just in case.

"But I didn't finish until 6pm and when I got to the police station at 6.15pm they had gone and closed.

"I thought, 'Do I leave it on the doorstep or put it through the letter box?'. I thought I had better not be irresponsible so I decided to take it back the next morning.

"But when the time came another job came up and it went in my shed. Then after about a week I told my wife I was going to get that grenade or whatever it was down to the police station. I showed it to the woman behind the desk and told her I wasn't sure what it was but I thought I should bring it in.

"She turned to her colleague and said something and he said, 'Where did you get that? Right everybody, out'. I've never seen anybody leave that police station so quickly."

Today police warned the public not to move suspicious objects, even if they look harmless.

In June the station was at the centre of a similar scare when a member of the public handed in several explosive devices found in the street.

They had been constructed using adapted fireworks.

A cordon was placed around the station while bomb disposal experts carried out a controlled explosion.

Detectives are still investigating where the devices came from.

Inspector Kim Hudson said: "This kind of thing does happen occasionally and while I wouldn't criticise Mr Welsh at all - he has done what he thought was right - I would warn people to leave these things and call 999 instead. "

Mr Welsh said: "I know I've wasted a lot of police time but I was doing what I thought was a public-spirited thing. I rang my wife and told her, 'I think I've caused a bit of a stir'. But the police were very nice and as they said, at least it gives them a bit of practice for that sort of thing."