Teams of hundreds have been working constantly for decades to patch up the many issues that regularly pop up at the Houses of Parliament (Picture: Getty)

Four centuries after Guy Fawkes was apprehended in the cellar of the Palace of Westminster, the biggest threat to the iconic Houses of Parliament once again lies underneath it.

But this time, the danger beneath the chambers is far less sinister and far more insidious.

It’s not active malice that is harming one of the world’s most famous buildings. It’s simply time. In the 150 years since construction was completed, it has deteriorated significantly, and efforts to patch up and mend any major issues that pop up have taken place constantly for decades.

There’s a serious risk that a faulty wire or leaky gas pipe could achieve what Fawkes never could.

Later this year, MPs will vote on whether they want to go ahead with one of the largest and most expensive restoration and renewal projects ever to take place in the UK. The aim is to replace the aging utilities and equipment that serves the Palace at the moment with something more up to date, and maybe cut down on the £1.4 million spent every week (yes, every week) on maintenance.

Nowhere is the crumbling infrastructure more obvious than below floor level.

Speaking to the University of Leeds academic Dr Alexandra Meakin for a thesis on the plans, former Lord Speaker Baroness D’Souza said the building was ‘a fire hazard of such enormous proportions that every day in Parliament thereafter when I visited the cellars, I was to think how lucky we are to have survived another day’.

To understand more about the problem and why members are considering spending billions on solving it, I took a trip to see the ‘guts’ of the Houses of Parliament for myself.

The Palace of Westminster still uses a sewage system that predates the one designed by Joseph Bazalgette for central London (Picture: Houses of Parliament Restoration and Renewal)

Descending the spiral staircase from ground level, I was immediately confronted with a clear example of the kind of logistical issue that complicates attempts to sort out the mess once and for all.

Above me was a gap in the ceiling, and beyond that, a crane. This, it turned out, was the only way to get anything in and out of the basement – a place with a mile of corridors, serving a building that covers the area of 16 football pitches. Doing work down there is a punishingly slow process, and if the single crane breaks, everything comes to a standstill.

The walls of the cellar are hidden behind masses of cables and pipes. When a new utility gets installed, the obsolete one is left behind because it would just be too complex to uninstall it. As a result, the layers take up a metre of space or more in front of each wall.

Wires that haven’t seen an electrical current in decades hang among the functioning ones. One disused water main pointed out to me was stamped with the year 1945. Hallways that should be wide enough for three people to walk along side by side are so narrow, it can feel claustrophobic going in single file.

The restoration project would strip out all the obsolete and unneeded utilities in the building (Picture: Houses of Parliament Restoration and Renewal)

And there’s something missing that seems so fundamental, I didn’t even think about it until it was mentioned later.

The UK’s corridors of power have no fire doors. Compartmentation – the practice of dividing spaces up with barriers to stop a fire spreading – is one of the most urgent requests of the people organising the Restoration and Renewal (R&R) project.

It is no coincidence that one building is mentioned again and again when MPs discuss the need for work on the Palace of Westminster: Notre Dame.

When the Paris cathedral was almost completely destroyed in an enormous blaze four years ago, it reminded politicians that the status of ‘internationally famous landmark’ is not enough to prevent disaster.

Speaking the day after the fire, then-Labour leader Jeremy Corbyn said: ‘You see beautiful buildings like that and think of the beautiful buildings we’ve got in this country. If any of those were destroyed in fire how would we feel about it?

‘The state of the building is very poor in Westminster and a fire risk is obviously huge with a building that has so much wood within it.’

The almost complete destruction of Notre Dame cathedral in 2019 struck fear into several British parliamentarians (Picture: AFP via Getty Images)

Andrea Leadsom, the Leader of the House of Commons at the time, said shortly afterwards: ‘Events like the terrible fire at Notre Dame bring home to us sharply the importance of preserving our historic buildings.

‘The Palace of Westminster, recognised the world over as a symbol of democracy, must be restored for future generations.’

For the moment, I was told a recently installed fire safety system means lives would not necessarily be at risk if a major fire was to break out. However, the future of the building itself depends on mitigation systems being installed before disaster strikes – otherwise, ‘difficult choices’ would have to be made.

There have been near-misses. In 2015, a malfunctioning light was noticed before it had the chance to spark a serious fire. Between 2008 and 2012, 40 small fires in the building were extinguished by wardens.

‘The Houses of Parliament are at risk of a catastrophic Notre-Dame style event,’ said Thangam Debonnaire, the shadow Leader of the House of Commons, who will help lead the R&R efforts if Labour win the next election.

Some original pieces of Victorian equipment, which survived the Blitz, can be seen in the basement (Picture: Houses of Parliament Restoration and Renewal)

She urged the government to help protect the thousands of people who work in the building, adding: ‘Labour is committed to the patriotic case for Restoration and Renewal.

‘One that provides value for money for the taxpayer, draws on the talents of people from across the county and secures a safe, accessible, and functional Parliament.’

And how much will that cost? Last year, the R&R Sponsor Body – which was later abolished and replaced with two parliamentary boards – estimated the work would cost between £7 billion and £13 billion, eye-watering figures even outside the context of a cost-of-living crisis. The total cost of the London 2012 Olympics is believed to have been somewhere around £9 billion.

However, I was told those numbers are now out of date. Considering the pace of inflation, it may be safe to assume they’ve only gone in one direction, but a new estimate is likely to be given to MPs before they vote later this year. In any case, there will be different costs for different options: anything from strictly the bare essentials to a complete facelift.

There is agreement on one thing – there is no ‘no cost’ option, short of leaving the Grade I listed building and UNESCO World Heritage Site to crumble into the Thames. There may not be much time, either.

Earlier this year, the Public Accounts Committee called for clarity on the timeline and potential price for completing the ‘massive job’ of saving the Palace of Westminster.

Committee chair Meg Hillier warned of ‘the real risk that the whole building will be destroyed by a catastrophic incident before the work is done, or perhaps even begun’, adding: ‘There are already people on decades-long risk watchlists after being exposed to asbestos in the building; a building that’s leaking, dropping masonry and at constant risk of fire.’

Like the pipes in Parliament’s basement, a great number of small fixes over time could have ultimately made the situation more complex. If MPs don’t want the decision to be whether they should rebuild a smouldering wreckage, they may have to confront a painful reality – as Hillier says, ‘before it becomes too late to do so’.

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Several MPs have expressed fear that the Houses of Parliament could be the next Notre Dame.