London's 'intergalactic' Shard opens to love and rain

A marriage proposal, strange similes and a stunning panorama marked the public opening of the viewing deck for western Europe's tallest tower on a wet day in London.

The Shard skyscraper was described as an "intergalactic spear" and a "cocktail stick" by charismatic Mayor Boris Johnson, who cut today the ribbon for the first public visitors atop the 310-metre futuristic tower looming over London bridge.

One visitor chose the moment to propose to his girlfriend of five years.

"It sounds corny but she makes me feel like I'm on top of the world so I thought the highest place in London has got to be the best place to do it," a smiling James Episcopou, 22, told reporters.

His fiancée, Laura Taylor, 22, said it had been a complete surprise.

"I just feel overwhelmed, surprised and the view is fantastic. It doesn't matter that it's raining."

The Shard is majority owned by Qatar and houses a premium hotel, several restaurants, 12 floors of apartments, 600,000 square feet of office space as well as the viewing deck.

It is part of a 2 billion pound ($3.17 billion) redevelopment of the London Bridge area on the south bank of the River Thames, which cuts through the British capital.

"All other buildings look like they've been put on the earth by people, but the Shard is like something that is prodding up," Johnson said.

"Prodding up through the frail integuments of the planet, like an intergalactic spear. It's like the tip of a cocktail stick emerging through the skin of a super colossal pickled onion."