Something mysterious is going on at Durham Cathedral.

Right now, Palace Green and the area around the cathedral are filled with equipment trucks, prop vans and security guards in a way that suggests some major filming is about to take place.

Durham Cathedral, however, has made no announcements about any movies being made and – when Durham Magazine checked the cathedral’s website today – there was no mention of any filmmaking going on.

But the cathedral is due to be closed to visitors because of “a major project”’ on the afternoon of Thursday 4th May and all day on Friday 5th May, Saturday 6th May and Tuesday 9th May.

Durham Cathedral’s Open Treasure exhibition will also be closed during these times, but the cathedral will be open for worship.

The suspicion is that part of the upcoming Marvel Studios film Avengers: Infinity War is about to be shot in and around the ancient building.

This rumour probably began after a tweet was posted in March showing directors Joe and Anthony Russo scouting for film locations in a place that looked very similar to Durham. The tweet has since been deleted.

Avengers: Infinity War, scheduled for release in May 2018, is set to feature stars such as Scarlett Johansson, Tom Hiddleston, Robert Downey Junior, Benedict Cumberbatch, Zoe Saldana, Samuel L Jackson and Chris Hemsworth.

There have been no reports – so far – of any of these stars being spotted in Durham’s streets.

But whatever is going on at the Cathedral seems to be shrouded in the greatest secrecy, with reports of people even being asked to delete any photographs they have taken.

Avengers: Infinity War is the sequel to the films Marvel’s The Avengers and Avengers: Age of Ultron.

In Avengers: Infinity War, the Avengers and the Guardians of the Galaxy come together to fight the villain Thanos, who is attempting to gather Infinity Stones: stones that will give him absolute power over space, time and all reality.

Filming has already taken place in Pinewood Atlanta Studios in Georgia and in Scotland, but maybe now Durham’s 900-year-old Cathedral will also be starring on the big screen.