If you wondered why the A42 between Ashby and Birmingham was closed over the Christmas and New Year break - this is the reason.

The route south from Ashby was shut between December 23 and January 2 - forcing motorists to look for alternative routes.

Burt time-lapse footage shows a 12,600 tonne HS2 bridge being 'slid' into place across a motorway in a world-first engineering feat.

Around 450 people spent 40 hours over the Christmas week slowly positioning the gigantic structure over the M42 in north Warwickshire - at a speed of four metres per hour.

HS2 Ltd believe the 165 metre 'box slide' carried out by their contractors is the longest of its kind to be achieved anywhere in the world.

The method involved building the entire 86 metre long bridge on land next to the motorway over a six-month period.

Civil and structural engineers then designed a sliding mechanism which allowed it to be pushed into place on a guiding raft between Christmas Eve and Boxing Day.

The Marston Box Bridge will be used to carry the HS2 high-speed railway on northbound routes in the direction of Crewe or towards Birmingham and London.

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HS2's civil delivery director, Mike Lyons said: "This is the first box slide of its kind over a motorway in the UK, and we believe it's also the world's longest slide, so it's a great achievement for HS2 as we quickly approach peak construction.

"It's fantastic to celebrate another big milestone for a project that is already providing work for almost 30,000 people today, and in the future, it will encourage people to use zero carbon public transport."

The operation took place during a ten-day closure of the motorway between Junctions J9 and J10 which is due to reopen on January 3.

HS2 claims the construction method, which allowed it to be moved into place in one movement, dramatically reduced disruption for road users.

HS2 and its contractor Balfour Beatty VINCI (BBV) said it worked in partnership with National Highways to deliver the 'intricate' operation.

National Highways senior network planner, Frank Bird said: "We'd like to say a big thank-you to motorists for their patience during the closure of the M42.

"It's never easy to close a busy motorway such as the M42 for an extended period of time but it has been vital to ensure the safety of the workforce and motorists while this work is taking place.

"We've been working collaboratively with HS2 for the past 18 months to ensure the operation ran smoothly and to help keep disruption to a minimum for drivers.

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"The installation of the new Marston Box bridge is a significant milestone in the HS2 project and it's great to see it finally in place."

Sasan Ghavami, Balfour Beatty VINCI's construction director, added: "We're extremely proud to have successfully delivered the world's longest box slide.

"It's a huge achievement for our project team and everyone connected with Balfour Beatty VINCI.

"We've used innovative construction techniques and worked tirelessly throughout the Christmas period to move this 12,600 tonne bridge over the M42 motorway – all done with the aim of keeping disruption to an absolute minimum."