It’s London’s most exciting archaeological dig. Except that nothing is being dug, and what’s being uncovered are not Roman treasures but the sometimes disconcerting secrets of the British building trade, circa 1949. Yes, this is the Royal Festival Hall as it hasn’t been seen since it was frantically constructed for the 1951 Festival of Britain: stripped to its concrete and stuffed with 30 miles of scaffolding and 300 construction workers.

Donning hard hat and wellies, The Times was given an exclusive tour of the hall — or the skeleton that remains, shrouded from public gaze — a third of the way through its £91 million, two-year refurbishment. It proved fascinating. What strikes you first is bareness. Carpets, seats, staircases and panels have disappeared — the latter to be restored as carefully as if they were priceless artefacts. Which, in a way, they are. The people who built the Festival Hall in post-Blitz Britain had huge problems getting hold of materials. So, with Herbert Morrison’s clout, they were allowed to requisition whatever wartime surpluses were lying around the docks. That included some extraordinarily fine American and Australian walnut and elm wood now impossible to replace from renewable sources.

Also gone, to everyone’s relief, is the asbestos — far more than anticipated. Removing it has pushed the hall’s reopening back to 2007, much to the irritation of London’s orchestras. But it’s not hard to see why the job has taken so long. A big area under the roof had to be hermetically sealed. Then, working in negative air pressure, highly skilled technicians removed the lethal stuff inch by inch, wearing protective suits, masks and breathing apparatus. Probably one of the most dangerous assignments in London.

The work in the auditorium beneath, though less hazardous, is no less fundamental. Its purpose is to remedy two glaring acoustical flaws: the musicians’ perennial complaint that they couldn’t hear themselves (Sir Simon Rattle famously declared that performing in this dead space “sapped the will to live”), and the lack of reverberation. The former is being addressed by remodelling the stage, pushing back the organ (which means redesigning the whole instrument), re-angling the side walls to reflect sound better and adding an adjustable canopy to enhance the vital high frequencies that define and clarify music.

As for the notoriously dry reverberation, that will be improved by rectifying a cardinal sin in the original design: a gap left between the hall’s wood panelling and its concrete walls, which meant that the panels absorbed sound like sponges. Now they are being fixed solidly to the walls.

Nobody is predicting precisely how much this will add to the reverberation time. But audiences should notice a difference. They will certainly notice another big change: the hall’s seating is being reconfigured to give everyone 35cm more space — a tacit recognition that the British waistline is not what it was in the war-rationed Forties.

Just as striking are changes being wrought in the foyers. Moving the hall’s bureaucrats into sleek new offices neatly tucked alongside the railway line will allow public access to many more areas. Most excitingly, a spectacular glass lift will carry punters up to two magnificent roof terraces. They were always intended to crown the building but haven’t been open to the public in living memory. The views are stunning: Parliament in one direction; St Paul’s in the other.

After the setback of the asbestos discovery, will there be any more hitches in this gargantuan architectural makeover? That’s impossible to say. But throughout the site the contractors have erected eye-catching notices reminding the workforce that time rushes past. “61 weeks to go!” the signs proclaimed when I visited. The urgency and excitement will mount as the months slip by.

Last chance to choose the Times/South Bank Show Breakthrough star

This is your last chance to vote for the Times/South Bank Show Breakthrough Artist of the Year. The polls close at 5.30pm today. The award will be presented by the Harry Potter star Daniel Radcliffe at the South Bank Show Awards on Friday, January 27, at the Savoy hotel in London. Among the presenters will be Ewan McGregor and Helen Mirren. The show will be broadcast on ITV1 on January 29.

The nominees are:

Film: Joe Wright
Literature: Diana Evans
Theatre: Ben Silverstone
TV drama: Billie Piper
Dance: Rupert Pennefather
Pop: M. I. A.
Classical: Julian Bliss
Visual art: Ceal Floyer
Opera: Kate Royal
Comedy: Mark Watson

Vote now at www.timesonline.co.uk/breakthrough, where you can also enter our prize draw for a pair of tickets to the event itself.

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