Apprentice Ben Nicholson thought he was in the firing line in his first week at work - after accidentally ordering a £2.7m battle tank.

Ben, 24, was looking for quotes for a water storage tank and was unaware his boss had slipped in a number for defence contractor BAE Systems.

So when he rang the Newcastle arms factory and asked for a tank coated with bitumen, there was initially some surprise.

But a member of staff at the tank builder realised Ben was being wound up and played along with the joke.

Later, he was horrified to receive an invoice confirming his order at the price of £2,785,994.27.

The outline specification stated the tank would have attached weaponry and equipment.

The letter from BAE Systems contained a brief apology to Ben, saying: "On this occasion, we are unable to paint your tank with bitumen as this would affect the camouflage.

"And although we could supply an equilibrium ball valve, this would be in lieu of the main armament and we felt it would render the vehicle somewhat ineffective."

Ashen-faced Ben took the letter to Nik Smith, his boss at Newcastle-based Gilwood Engineering, expecting to be handed his cards.

Business development manager Mr Smith said: "He was very worried indeed. He was wondering what he had got himself into.

"Someone at the other end of the line obviously realised he was being wound up and played along with the joke."

Ben said: "Apprentices are often sent out for sparks for the grinder or tartan paint - but this takes things to a completely different level."