Motorists have been warned of four weekend closures this summer on the M42 as HS2 prepares to install beams on its 'twin box' structure.

HS2 engineers are ready to start installing the beams on the structure that will span both carriageways of the M42 near Solihull.

Once complete, vehicles will drive through the 300-metre-long 'twin box', while trains travel above.

Over a series of four separate weekends in June, July, August and September, 175 prefabricated beams will be installed, each weighing between 56 and 92 tonnes.

The 23-metre-long beams will be lifted into position using a 300-tonne crawler crane, effectively bridging the gap between the supporting walls and columns.

The first closure will take place from 9pm on Friday 26 June until 5am on Monday 29 June.

It will be in place between junctions 5a to 7 northbound and 6 to 7 southbound.

HS2 said the "scale and complexity of the operation" means the beams can only be moved if the road is closed.

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Two supporting walls have already been built on either side of the carriageway.

Inside the central reservation, a central pier of 46 supporting columns is almost finished.

The 10-metre-high walls have been built using prefabricated hollow blocks, likened to giant Lego bricks.

Weighing an average of 14-tonnes, each block was lifted into position and stitched together using reinforced concrete to support the 9,800-tonne beamed roof.

With the walls now structurally complete, engineers working for HS2's construction partner, Balfour Beatty VINCI (BBV), will turn their attention to the next significant phase - the beamed roof installation.

Agnes Usciak, HS2 Ltd's Senior Project Manager for the works, said: "This is a huge moment for the project, and a clear sign of the progress we are making as we begin bridging the gaps over the region's motorway network.

"This is British engineering at its very best, and it's fantastic that a UK-based firm has led the way in developing this innovative design solution for the twin box, with manufacturing taking place in the Midlands."

A team of 180 engineers and specialists from BBV and Expanded will lead the installation.

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They will work in shifts, around the clock, to ensure phase one is completed in time for the motorway to reopen at 5am on Monday, 29 June.