Within the wood paneling of a hallway in the British House of Commons, there was a small brass keyhole.
Members of Parliament and staff walked past the tiny hole each day. The rare person who noticed the hole took it for an electrical cabinet.
Enter a team of historians planning the much-needed restoration of the Palace of Westminster, which is home to the House of Commons and the House of Lords. The oldest part of the estate, Westminster Hall, dates to 1099 and is still in use.
The team was at the Historic England Archive poring over some 10,000 uncatalogued documents relating to the palace when they found something interesting: plans for a doorway in the cloister behind Westminster Hall.
Back at the palace, they found that tiny keyhole in the wood paneling — just where the plan suggested it would be. They had a key made so they could open the door – and they discovered a secret passageway 360 years old.
"To say we were surprised is an understatement — we really thought it had been walled-up forever after the war," Mark Collins, Parliament's estates historian, said in a statement. They knew such a passage had once existed, but believed that it had been filled in after the palace was bombed during World War II.
Behind the door was a small room, with hinges for a door that would have been more than 11 feet high and that would have opened into Westminster Hall.
It turns out to be a passageway with a rich history.
Investigators studied the ceiling timbers in the room and determined that the trees had been harvested in 1659. That corroborated accounts suggesting that the doorway was created around 1660, for the coronation banquet of Charles II, the king who ruled until 1685.
Records indicate the route was used by part of the coronation procession as it passed from the former House of Lords into the hall where the king and queen were seated. Afterward, the door was used for coronations, the Speaker's procession and, more commonly, by members of Parliament to access the Commons chamber.
Historians say the entrance was used for centuries, by figures including the diarist Samuel Pepys, Robert Walpole (now regarded as the first British Prime Minister) and William Pitt the Younger.
In the passage, the team found more-recent artifacts: graffiti from 1851.
A bricklayer who was restoring the palace years after an 1834 fire had written on the walls in pencil: "This room was enclosed by Tom Porter who was very fond of Ould Ale."
Another bit of graffiti read: "These masons were employed refacing these groines [repairing the cloister] ... August 11th 1851 Real Democrats."
The term "Real Democrats" suggests that the masons were supporters of the Chartist movement for universal voting rights for men and to allow for members of Parliament who weren't property owners.
House of Commons Speaker Lindsay Hoyle paid a visit to the newly discovered passageway, one used by his predecessors over centuries.
"To think that this walkway has been used by so many important people over the centuries is incredible," he said. "I am so proud of our staff for making this discovery and I really hope this space is celebrated for what it is: a part of our parliamentary history."
And evidence of more recent history was found in the passage, too: a working light bulb, likely installed in the 1950s.
That tiny keyhole in the wood paneling turned out to be a portal to Britain's history — found again, after 70 years unnoticed.