The London Underground’s book exchanges could be saved after Sadiq Khan stepped in over TfL’s decision to scrap them.

Transport for London (TfL) axed the mini-libraries on Tuesday, which first appeared in the capital around 20 years ago, over fire safety concerns.

The shelves encouraged commuters across the network to take a book for free or leave one for somebody else to enjoy.

But this week, a sign appearing in several stations across London read: “Due to fire safety regulations from the London Fire Brigade, we have been forced to close all book exchange libraries.

“[This] is on all London Underground stations with immediate effect. We are all sad to see this go. Thank you for all your support over the years.”

But the Mayor of London has now stepped in to reverse the decision, The Independent understands.

A source close to Mr Khan said TfL was urgently working with the London Fire Brigade to ensure the shelves were reinstated.

One commuter wrote on social media on Tuesday: “Wow… just wow. My local tube stop Oval had a great little public book exchange sat near the gates.

“But apparently despite being there for years the meddling bureaucrats have decided a couple of books near a tiled wall are a fire hazard. Why can’t we have nice things?”

London’s first recorded TfL station book-swap was set up in 2005 in Raynes Park, after a nearby library was being refurbished and wanted to offload some stock.

Around five years later, Anthony Fairclough, who was then a legal researcher and chair of Merton Liberal Democrats, set up an exchange in Wimbledon.

This inspired Chris Gilson, then a committee member of West Ealing Neighbours, to set up a similar initiative at West Ealing Station.

In December 2011, the Books for London campaign, which helped establish the network, was the winner of the first #ideas4Mayor competition at the London Policy Conference. It was then officially launched and spread across the London Underground ahead of the 2012 London Olympics.

Former Mayor of London, Boris Johnson, said at the time: “I think it’s a very good idea and would say something powerful about the kind of city we are.

“And to our commitment to literacy, which obviously we are trying to demonstrate in lots of ways particularly with young people.”

A London Fire Brigade spokesperson said: “Ensuring the safety of those using the London transport network is our priority.

“We are working with TfL with regards to their responsibility to remove all book libraries from subsurface stations.

“This is due to combustible material posing a fire safety risk if it is stored on these premises. Non-subsurface stations have been asked to remove book libraries from display until they have the correct fire safety plans in place.”

A spokesperson for TfL told The Independent: “We work very closely with London Fire Brigade and other emergency services to ensure our services run safely and following guidance from the fire service, we have advised our staff to remove book swaps from stations.

“We’d like to apologise to any of our customers that this impacts, and we are reviewing our processes for these internally and will work with the fire service to see if book swaps can be re-introduced at some stations across the network in the future. We will also work with local communities to redistribute books to alternative local locations in the meantime.”