Most motorists in Kent have travelled along the 50.6-mile M20 at some point or another but have you ever thought about how it was built?

It was billed as a new way to get around in the 60s and 70s, and changed Kent's landscape forever, and is now used by millions of drivers each year.

So we thought we'd take a look back at its history from new junctions and bridges being built or dismantled to its new Smart Motorway section to the controversial Operation Stack and Operation Brock, which will again affect the motorway as the country leaves the European Union this winter.

The motorway is like many others built in the UK, it was opened in stages and runs from the A20 at Swanley , meeting the M25, and continues to Folkestone and provides a link to the Channel Tunnel and the Port of Dover.

Construction started more than 70 years ago, with junctions 5 at Aylesford to junction 7 at Maidstone.

These sections were officially opened in 1960 and at this point, the motorway was known as the Maidstone Bypass and the road was numbered as the A20(M) as it bypassed a stretch of the A20 (then the A2020) in Maidstone.

It was the first stretch of motorway to open south of London and, despite not opening until 1960, plans had existed for it since the 1930s but were not upgraded to 'motorway standard' until the 1950s.

Junction 7 at Maidstone to junction 8 at Maidstone East opened in 1961 but later, when the motorway was extended westwards towards London in the 1970s, it was renamed M20 and the A2020 reverted to A20.

Junctions 3 for the M26 and Sevenoaks to junction 5 for Aylesford were completed in 1971.

In March 1971, a man was killed and 15 were injured when a bridge spanning an uncompleted section of the A20(M) motorway, between Coldharbour and Wrotham Heath, collapsed.

The bridge, at the Leybourne interchange, was one of 16 being built in a £4.4million contract for six-and-a-half miles of dual carriageway.

About 20 men were on the bridge when the 116ft centre span began to sway. Within seconds the metal, concrete and hardcore collapsed 40ft on to the motorway beneath, taking the men with it.

Junction 1 for Swanley and junction 2 for Gravesend , Tonbridge and Wrotham were not completed and opened for another six years, until 1977, and this section ended at a temporary junction near West Kingsdown and a temporary terminus to junction 3 at West Malling was completed in 1980.

In 1981 junction 11, where the M20 crosses the A20 at Sellindge, to junction 13 for Folkestone were built.

In the same year an Old Barn in Hollingbourne near junction 8 had to be demolished to make way for a section of motorway.

The section around Ashford, junctions 9 to 10, was originally the A20 Ashford Bypass, with construction having started before the Second World War, although the route itself was not opened until July 1957.

The bypass started at Willesborough near the current location of junction 10 and terminated south of the existing junction 9 at the current Drover's Roundabout.

Junction 10 of the new motorway at Willesborough saw an array of homes demolished in the area to make way for the new stretch of motorway.

At this point, this left the motorway in two sections, with the 14-mile gap running via the A20 and was known locally as the Missing Link.

At the time, levels of traffic were not considered high and it was not necessary to complete the route as most traffic was then using the A2/M2 route to get to the Channel ports.

When it was announced the Channel Tunnel was ready for construction, it was then decided the M20 would be completed.

Junction 8 for Maidstone to junction 9 for Ashford opened in 1991 and at the same time an extension to Dover, as part of the A20, was also constructed and opened in 1993 and a new junction, 11A was also built for the Channel Tunnel.

Following completion of the junction 8 to 9 section, the M20 was three lanes, but later it was decided to widen this section to four lanes and this was completed in 1995.

More recently, between 2006 and 2007, junction 10 near Ashford was remodelled.

Bridges across the motorway were modified to provide three lanes of traffic at the roundabouts, and local approach roads were widened, with new traffic lights to control traffic flows at the junction between the A292 Hythe Road and the London-bound M20 entry slip road.

In August 2016, a pedestrian footbridge was brought down by a lorry between junctions 4 and 3.

The southern section of the bridge - which rested on a plinth - was dislodged and fell onto the carriageway below, landing on the trailer of a passing HGV.

Both carriageways of the motorway were closed so the broken section could be removed that September.

A new footbridge was also constructed across the motorway at a cost of £4.9 million .

And in West Kent between junction 4 and 7 variable speed limits were introduced.

In July 2018, work started between junction 3 to junction 5 to turn this section of the motorway into a Smart Motorway .

It uses the latest technology to sense traffic flow and set speed limits which is aimed at keeping traffic moving smoothly to prevent queues and the design involved converting most of the hard shoulder into a traffic lane to create extra capacity.

Watch KMTV reporters trying out the Smart Motorway section of the M20

A proposed new junction 10a at Ashford was originally announced by the Highways Agency in May 2012.

Work on it was postponed until planning for it started again in 2016.

Construction work started in January 2018 and a new bridge was also built and the coast-bound slip roads at the existing junction 10 were closed to allow the final works on the London-facing slip roads for Junction 10a to be completed and the new junction opened on 31 October 2019.

Operation Stack, which was first introduced in the late 80s, is a scheme which has had to be used on the motorway after the opening of the Channel Tunnel.

Sections of the motorway have had to be used on occasion when there is disruption at the Port of Dover or at the Channel Tunnel. This sees part of the motorway closed and used as a lorry park.

Operation Brock replaced Stack a few years ago and was to be used in the event of a no-deal Brexit, but after the UK left the EU and in anticipation of disruptions at our ports, the government announced Op Brock would be rolled out again this winter.

The scheme led to a barrier being put up along a large section of the M20 between junction 8 for Maidstone and junction 9 for Ashford .

Highways England workers laid out 7,500 cones and 350 signs before the scheme could be activated.

The Operation Brock contraflow saw the carriageway between junction 8 for Maidstone and junction 9 for Ashford restricted to two lanes for nearly a year, at a cost of more than £35m to the taxpayer.

Work to remove the barrier, installed as part of preparations for a no-deal Brexit, had been completed just in time for Britain's exit from the EU.

After Op Brock was removed in early January this year, seven months later, it was revealed it was set to return but this time moveable concrete blocks would be used instead of the previous metal barrier that took a month to put in and remove.

The impending return would cost a mammoth £55m , it was revealed earlier this month.

Highways England has awarded contracts to Lindsay Transportation Solutions and Balfour Beatty to carry out work on the 15-mile stretch of road.

The barrier will be installed and become operational in December - in anticipation of disruption once the Brexit transition period ends.

Once up-and-running, the barrier, which road chiefs say can be installed within hours thanks to a specialist ‘zipper’ machine, will result in a 50mph speed limit.

Operation Brock is set to return this December

The last changes announced which affect the M20 were made in July this year when the government said it had bought a site beside junction 10A to build the Sevington customs clearance facility and lorry park .

Work started on the post-Brexit lorry park in Ashford , just hours after it was announced the government had purchased the site.

Contractors moved in on the 27-acre spot as ministers prepare for the end of the Brexit transition period in December.

The lorry park holding area is being built in case there is disruption at Dover and as a border control post to check truckers have the correct paperwork.

But dejected residents living close to where the huge post-Brexit lorry park is being built say the realities of Britain leaving the EU have now sunk in.

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