29 October 1986: The M25 motorway is opened

As far back as 1911, planners had been proposing a ring road around London. By the 1960s they were proposing four concentric ring roads – the London Ringways – plus a whole lot of radial routes in and out of the city.

Construction was started on the series of urban motorways, and the Westway and the East Cross Route were completed before everyone came to their senses. London escaped the fate of being concreted over into some US-style freeway-ridden hellhole.

But some of the plans lived on. Ringway Two would eventually become the north circular road, and ringways three and four would morph into everyone's favourite orbital road, the M25 motorway.

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Construction started on the section between South Mimms and Potters Bar in September 1975. But before the bulldozers could move in, there was rather a lot of sorting out to be done.

There were 39 Public Inquiries, which sat for a total of 700 days. Archaeological digs had to be funded: two Bronze-Age settlements and a 9,000 year-old Stone-Age settlement were unearthed, and over 200 Saxon graves were found at a burial site in Kent.

A thatched cottage was dismantled brick by brick and reassembled out of the motorway's path, at a (now very reasonably-sounding) cost of £70,000. The Epping Forester Cricket Club had to be put up at an alternative location while the motorway was built underneath their pitch (they must now surely be the only cricket club in the world that plays their home games on top of a motorway).

The total cost was £909m (£5.8m of that came from the EU). With the motorway 117 miles long, that works out at £7.5m per mile.

Eventually, 11 years after it was started, the final 13-mile section between Micklefield Green and South Mimms was finished. The prime minister cut the ceremonial ribbon, and the traffic began to flow.

Not too long after opening, however, the traffic stopped flowing. The road was operating at beyond its maximum capacity. And so the battle to keep up with demand began, with widening schemes, variable speed limits, and a new bridge across the Thames being constructed to keep the endless stream of traffic moving.