Mike Hume was on scaffolding 40ft (12m) above the stage when he put his hand in a gap behind an ornate crown decoration and found the century-old bottle.

After months of painstaking effort, experts extracted the note from inside and found a list of the people who built the theatre in 1906.

Mr Hume, one of the theatre's donors, made the find while on a tour of its £40m restoration works.

The 48-year-old said curiosity caused him to reach behind the crown. "It was like a scene out of Indiana Jones," he said.

"It was a bit damp and there was all this crumbly plaster and stuff in there - then my hand stumbled on this solid object and I pulled out this glass bottle."

Although the top of the bottle had been dipped in plaster, to keep it sealed, Mr Hume could see a note inside.

The note contains names of the contractor, builder, architects, draughtsman, foreman, and plasterers.

Abby Pendlebury, the theatre's heritage engagement manager, said finding the bottle was "incredibly thrilling". "I think it is fascinating we have a list of plasterers and draftsmen," she said.

The King's Theatre cost £50,000 to build in 1905. The current redevelopment, which started in 2022, will cost £40.7m.

Two lifts are being fitted, and staircases are widened in the category A-listed theatre, which Capital Theatres manages.

The auditorium is being redeveloped, a wall is being reinstated and a new control room is added.

The gantry is being upgraded with a lighting system and will soon receive a new ventilation system.