Must have a head for heights! London's Tower Bridge unveils £1m glass walkway 140ft above River Thames... costing just £9 to visit

There's a word to describe moments such as this and I think it’s probably… eek!

The waters of the Thames are rushing 138ft beneath me and a double decker bus on the road below resembles a scale model.

The pedestrians milling about on the pavements look as if they have come to life from a Lowry painting and there is nothing between them and my boots but a sheet of glass.

It sounds like a scene from Hitchcock’s Vertigo – but it’s the latest attraction at Tower Bridge. And yesterday I joined hundreds of pioneers to look down on London through a glass walkway on the upper part of the bridge.

The time-honoured advice when you’re this high off the ground is not to look down. Too late though. I already did.

Scary? Only if you’re truly terrified of heights. But the unexpected shock of suddenly seeing what appears to be only fresh air between you and certain death did give a few the collywobbles.

Especially when a chirpy Tower guide jumped vigorously up and down on the glass alongside us to demonstrate (what we hoped was) its resilience. 

One half of the £1million walkway opened to the public yesterday between the north and south towers of the bridge and will be joined on December 1 by a parallel walk alongside it.

They have been designed to give tourists, sightseers and thrill-seekers a unique view from a bridge that bills itself as the most famous in the world, not forgetting a peek at the workings of a legendary feat of engineering when the bridge below opens.

For the faint of heart or weak of knee, it may be reassuring to learn that each glass panel along the 36ft walkway is getting on for three inches thick and weighs nearly 1,200lb.

Tower Bridge Exhibition executives insist the idea is to enthral rather that scare people – but this might not have been clear to some of those taking their first steps into the unknown yesterday.  

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Never-before-seen views: A boat passes under Tower Bridge's new glass floor after it was unveiled on Monday

‘Everything in your brain is saying “don’t, don’t, don’t”,’ said Stan Cooper, a 71-year-old retired fireman from Corfe Mullen, Dorset.

‘I trained on 100ft turntable ladders but at least you’ve got something you can see beneath your feet. Here, your eyes tell you you’re walking on thin air.’

Kristy Jones, 36, from Leeds, used the experience to confront her fear of heights. She walked the entire length of glass, speeded up only towards the end – and yes, she did look down. 

‘It was pretty frightening but I don’t like to let it beat me,’ she said. ‘I can’t take too much of it.’

Not so for Magdalena Sirola, nine, and sister Veronica, six, visiting Tower Bridge with their mother Andrea. They twirled, jumped, danced and slid fearlessly on the glass for more than 20 minutes, lying down at one stage to wave to the people below.

Ah yes, the people below. Would they be able to use their vantage point for an up-skirt snapshot of unsuspecting women above? It is something the bridge’s architect Sir Horace Jones and civil engineer Sir John Wolfe Barry did not have to consider 120 years ago – but the walkway designers admitted that they did.

A guide tells me: ‘At night it will be illuminated with so-called “modesty lighting”. In the day, the reflection, distance and angle mean the view upwards from beneath is nothing like as clear as the view downwards from above. We don’t expect to see crowds gathering on the pavements.’