FILE PHOTO: Yeoman Warders interact with tourists at the Tower of London in London, Britain, July 20, 2017. REUTERS/Neil Hall/File Photo

LONDON (Reuters) - The Tower of London’s colorful “beefeater” guides are to go on strike next month over pension changes, their GMB union said on Friday.

They will be joined by colleagues at Hampton Court Palace, Henry VIII’s opulent residence further up the River Thames, after a ballot for strike action was 91 percent in favor.

Pickets will be out at both buildings, run by Historic Royal Palaces (HRP), on the day of the 24-hour strike, Jan. 8.

“HRP are jumping on a bandwagon which is seeing employers engaging in a race to the bottom, ending good final salary schemes and replacing them with risky cheaper defined contribution schemes,” said GMB regional organizer Michael Ainsley in a statement.

Three 3-hour walkouts at HRP sites are also being staged by members of the Public and Commercial Services Union (PCS) from Friday.

HRP said the sites would stay open during the action.

“Although we fully respect the rights of trade union members to take industrial action, (the) strike is disappointing,” said Chief Executive John Barnes. “However, it will not change our decision to close the Defined Benefit scheme,” he added.

The famous yeoman warders have been guarding the Tower of London since the 16th century and may have got their name from the days when part of their salary was paid in beef.

Their distinctive red uniforms, known as the state dress uniform, is worn on state occasions such as the monarch’s birthday. A more durable everyday dark blue uniform was introduced in the 19th century.