The M4 50 years later – and how it all started in Maidenhead
The London-South Wales motorway – later known simply as the M4, along with the European route E30 – crosses Berkshire as it winds west for 189 miles from London.
It carries 130,000 vehicles a day, connecting towns and two countries across the UK – but its origins are here in Berkshire.
the RAC website says it was completed between 1961 and 1996, but this summary hides a surprisingly complex story. In fact, the M4 originated in Berkshire – which is not widely recognized.
Construction of a bypass at Maidenhead actually began before the war, guided by what was then Berkshire County Council. The 19 mile stretch was built by Costain Civil Engineering Ltd, a company founded in Maidenhead in 1865.
It was one of many such roads intended to be merged into the new motorway, according to a major 1,000-mile plan by the Department for Transport to modernize UK motorways.
After a pause throughout the conflict, construction of the Maidenhead Bypass resumed in 1959, joined soon after by its close neighbor – the Slough Bypass.
A total of 63 miles had been run in 1967, with the reading section – from Exit 9 at Maidenhead to 15 in Swindon – being opened by Congressman Henley Michael Heseltine on December 28, 1971.
A free flow junction built at Winnersh by W&C French Ltd – a company that also built portable and prefabricated ports for D-Day landings – provided easy access from the M4 to Reading.
Maidenhead was also where the M4 took another milestone, with the opening of a 50 mile stretch between Badbury and Maidenhead in 1971, completing a 139 mile continuous stretch of motorway between London and the South of the Country of Wales.
The Welsh section was completed in 1993 with the opening of the Briton Ferry motorway bridge. The Second Severn Crossing opened in 1996, slightly diverting the road and shaping the M4 as it is now known.
Why was the M4 built?
Without the M4, Wales’ recovery from WWII could have been even longer and more arduous than it was.
Connected to England only by the A48, with its many hills and sharp bends, traffic between the capitals of the two nations was vulnerable to traffic jams and long delays.
A motorway from London to Cardiff was first considered in the 1930s – two decades (and a war) before the opening of Britain’s first motorway (the Preston Bypass, in 1958).
Its construction dramatically sped up the movement of people and goods, leading Welsh historian Dr Martin Johnes to call it the most important place in Welsh history.
It also provided much-needed jobs for thousands of war-weary young men returning from years of fighting in Europe, Africa and Asia.
The digital quirks of the M4 – and a piece of WWII history
The M4 has not been universally welcomed, including in Berkshire, where residents of Winnersh have protested its early construction on the grounds of anticipated noise pollution.
Love it or hate it, the highway is special in many ways. It has two of the only three four-tier interchanges in the UK – at Junctions 4B and 20.
It also features the only junction in Britain with two numbers: the 8/9 junction, near Maidenhead in Berkshire.
This situation arose when the freeway was finally joined, diverting it from the existing junction 8, where the road ended. This threatened to cause numbering problems further west, so double-numbering was adopted as a quick fix.
A similar digital quirk occurs at junction 31, near Cardiff – or rather it isn’t, as there is no junction 31. Given the building permit in 1991, it never did. was built due to local opposition.
In April 2008, clearing of shrubs on the banks of the highway at Great Lea Common, Berkshire, revealed a Vickers machine gun pillbox, which was among the last British defenses in the event of a German invasion.
Rather than cutting it down, as initially planned, the promoters of the road decided to preserve it as a bat roost.
How the M4 has changed over the years and future projects
Between 2008 and 2010, Reading Junction 11 was extensively renovated for around Â£ 65million, with a new four-lane junction and two new road bridges.
This involved the relocation of the Local Roads Agency and fire service offices, as well as the construction of a long network of walkways, a new bus lane and a new roundabout.
Further west, in February 2010, it was announced that the M4 in South Wales would become the first hydrogen motorway, with hydrogen stations along the route.
It was expected that more such stations would expand into England over time, until hybrid and all-electric cars saw hydrogen cars following Betamax’s path.
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The West Berkshire section, near junctions 12 and 13 for Hermitage, saw bridge renovations in 2017-18, with the full width closed on weekends as huge cranes laid the new bridge deck beams .
And the route is currently undergoing a smart upgrade of its eastern sections, between Junctions 3 and 12 – including its Berkshire section – at an expected cost of Â£ 860million, according to the RAC.
The upgraded M4 will use the latest technology to monitor the flow of traffic and set speed limits, allowing traffic to move smoothly rather than continually stopping and starting.
The hard shoulder will be converted into a traffic lane, giving the highway four lanes in each direction (five between Junctions 4 and 4B). And the central separator will be replaced by a concrete barrier.
The Highways Agency says these changes will reduce congestion and improve travel times, supporting economic growth in the region while improving both the safety and environmental impact of the road.