The Queen came face to face with a 7ft purple dinosaur, a portly penguin and a larger-than-life construction worker yesterday in one of the strangest Royal line-ups ever.

Despite the unusual dignitaries, she was unfazed as she met Bob the Builder and other colourful characters from the world of children's TV.

As Bob stood with his friends, Barney the dinosaur and Pingu the penguin, towering above the Queen, he offered his large palm to the visiting Royal, who shook his hand and said with a smile: "Good morning".

Bob dressed down for the occasion, wearing his familiar dungarees and yellow hard hat.

But he did get a bystander to adjust his low-slung tool belt shortly before the Queen arrived.

She was visiting children's television producer HIT Entertainment, in London, as part of a Royal theme day to celebrate British enterprise.

The Queen asked a group of excited youngsters standing close to popular favourite Bob: "Do you know this person? Do you watch him?"

While Barney has in the past kept the company of Bill Clinton, George Bush Snr, Nelson Mandela and Dolly Parton, Bob is said to be seen rather less on the celebrity circuit.

"He doesn't usually mix with celebrities. It's a big day for him," HIT spokesman Simon Forrest said.

Bob has, however, previously met Prime Minister Tony Blair, at Millbank.

Mr Forrest said that, prior to the visit, a collection of books, stuffed toys and videos were sent to Buckingham Palace so the Queen could brush up on the family of characters.