LONDON – London’s legendary blue plaques -- historical markers commemorating the lives of eminent figures -- face an uncertain future because of austerity cuts at England’s official heritage agency.

More than 850 ceramic signs honor key people who lived in the U.K. capital, and their contribution to human history.

Toby Melville / Reuters (file)

One of London's 869 blue historical markers.

But the program -- almost 150 years old and believed to be the first of its kind in the world -- now faces a “very uncertain future,” according its lead administrator at English Heritage.

“These are extremely difficult times for English Heritage and for the scheme,” wrote Emily Cole in a letter made public earlier this month.

Existing plaques will remain, but no new locations are planned and the panel of historians and experts that considers nominations for future signs has been suspended.

The news has been greeted with dismay in London.

“Blue plaques are one of the most charming ways a capital has ever found to preserve historical memory,” cultural commentator Jonathan Jones wrote in The Guardian newspaper. “They eschew the pomposity of statues.”

David Tucker, who leads thousands of tourists on guided walks of London every year, told NBC News: “The plaques are part of the fabric of the city and it’s such a shame.

“As an American living here for 30 years, I can say that I still find myself coming across plaques I have never seen before and learning new things.”

The earliest surviving plaque, erected in 1867, marks the building in King Street where French emperor Napoloeon III once lived. (The first, erected the same year to commemorate the birthplace of Lord Byron, was lost when that building was demolished in 1889.)

In total, the city is dotted with 869 circular, domed signs. Among those honored are Americans with London connections including Jimi Hendrix -- who lived on Brook Street while recording 'Electric Ladyland' -- author Mark Twain, inventor Samuel Morse and broadcast journalist Edward Murrow.

Similar historical markers now exist elsewhere in England in many other cities around the world, including in the United States through bodies such as the New York Landmarks Preservation Commission.

“Over the next eighteen months, we will work up the details of a new and more cost-effective approach to its administration,” said Ellen Harrison, a spokeswoman for the English Heritage, adding that it would need to “become more cost effective and more self-sustaining.”

Each sign costs $1,500 to manufacture and a further, variable, sum to install, while the overall program costs $400,000 a year to operate.

English Heritage last year generated around $86 million from membership subscriptions and admission fees at its historic sites. But it is still heavily reliant on public cash, and faces a 34 percent cut in its grant from Department for Culture, Media and Sport, from $218 million in 2010 to $147 million in 2014, as the U.K. government struggles to reduce a huge budget deficit.

One plaque marks the site of the studio used by sculptor Sir William Reid Dick, who wrote that buildings are “more than just bricks and mortar…they are the theaters in which our lives are enacted.”

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