Woodpeckers and rot are being blamed for the demise of a flagpole which was once the tallest in the world.
The 225ft flagpole entered the Guinness Book of Records in 1959
A team of steeplejacks began dismantling the Kew Flagpole in Kew Gardens, south-west London, on Monday because it was unsafe for flag-flying.
The wooden structure has already had to be shortened several times.
It entered the Guinness Book of Records in 1959, when it measured 225ft (69m). Metal flagpoles, however, can now reach greater heights.
"Sadly our historic flagpole, once the tallest in the world, is no longer safe for flag-flying," said David Holroyd, head of estates at Kew.
"Woodpecker action and decay have made it unsafe, so we have no alternative but to dismantle it - and it will be a major operation."
Steeplejack Mark Meager said: "You've got a lot of things to think about. People's safety, obviously, which is the main thing.... where it's going to land and where it's going to swing to."
Mr Meager said cutting the pole was "quite intense" and "tiring".
Even though it is the fourth flagpole on the site since 1861, there are no plans to replace it.
Mr Meager said: "It's one of the special views over London, you can see the Thames, you can see right into the city, see Canary Wharf, right over into Buckinghamshire.
"On a sunny day, it's really nice."
A decision on what to do with the pole's remains has not yet been made.