The two-tonne probe, named after the ancient Greek mathematician Euclid, will be heading towards an area in space known as the second Lagrange point, where the gravitational forces of Earth and the Sun are roughly equal, creating a stable location for the spacecraft.

The UK has contributed £37m towards the £850m mission, with scientists playing key roles in designing and building the probe and leading on one of the two scientific instruments on board.

The aim of the mission is to shed light on two of the universe’s greatest mysteries: dark energy and dark matter.

Professor Tom Kitching, of UCL’s Mullard Space Science Laboratory – one of four science co-ordinators for Euclid - said: “The puzzles we hope to address are fundamental.

“Are our models of the universe correct? What is dark energy? Is it vacuum energy – the energy of virtual particles popping in and out of existence in empty space?

“Is it a new particle field that we didn’t expect? Or it may...