The main lower mast of Nelson’s flagship HMS Victory has been removed for the first time in nearly 130 years for essential conservation work.

The removal of one of the earliest surviving examples of a wrought iron mast in the Royal Navy is part of a 20-year conservation project on the warship based at Portsmouth Historic Dockyard.

The three-day operation involved a huge crane lifting the 26 tonne mast structure “at a snail’s pace” through the ship’s four decks from its anchor point in the orlop deck where it had been secured since 1894.

The original masts used for Victory were wooden but a survey in 1893 found they were rotten and they were replaced with wrought-iron masts from the decommissioned HMS Shah.

Andrew Baines, HMS Victory project director at the National Museum of the Royal Navy, said that the three lower masts, made in Portsmouth, were important artefacts and are believed to be the only surviving 19th century iron masts still in use.

He said: “Removing the lower mainmast has been an incredibly complex project.

“Add in HMS Victory’s iconic status, her age and our desire to keep her open to visitors as much as possible, and we have been faced with some unenviable engineering challenges.

“We have conducted ultrasonic thickness testing on the mast to understand its strength.

“Structural analysis has calculated the stresses in the mast from the lift and allowed us to develop a method to keep them within allowable, safe levels.

“We then needed a clear three-day window for both the 500 and 200 tonnes cranes to manoeuvre the mast from the ship, hoist it aloft 42 metres, and then place it safely alongside where we can analyse it further and agree on the next steps.

“We know how strongly our visitors feel about Victory being without masts, but it is essential that we are able to complete this next stage of conservation, so she can remain open for the next 250 years.”

He added that analysis of the mast will determine whether the remaining masts would also need to be removed for similar conservation work.

HMS Victory and the other attractions at the Portsmouth Historic Dockyard including the Mary Rose Museum are set to reopen on Monday May 17, following lockdown easing.