The M11 most famously connects London to Cambridge in a major route north.

But oddly, it begins at junction four – a road in South Woodford which is elevated for no apparent reason.

The strange quirk has been explored in a new video by Jon Jefferson of Auto Shenanigans.

The YouTuber shot to fame for delving into the stories behind some of the country’s most interesting roads.

Now, Jefferson has revealed the secrets of the unusual bridge – it was initially part of an ambitious urban motorway project that would have ended in the capital.

The M11 was completed in 1980, beginning at South Woodford. But while the decision to start the motorway at junction four might raise eyebrows, it actually makes sense.

There were once plans to extend the road further into London. These extensions, including junctions 1 to 3 and the M12 motorway, were part of the infamous London Ringways project – an extensive plan to build a network of motorways across the capital, which would have involved demolishing large parts of the capital.

However, the project was cancelled before completion. And by the time the decision was made to wield the axe, some sections of the M11 had already been built, including the mysterious bridge.

It wasn’t simply a case of poor planning, Jefferson explained, but rather the result of a huge infrastructure project being abruptly halted.

He explained: “Sure, millions had already been spent on feasibility studies, planning and building some parts of the Ringways Project. But this was pocket change compared to the cost of the completed project.

“So the entire scheme was cancelled with immediate effect which leaves us with what appears to be a bridge over nothing and an interchange that if you were to build it today wouldn’t look anything like this.

“It’s truly bizarre but as we’ve learned there’s a reason why it’s like this – it wasn’t the road builders and planners just having a laugh, it was because a huge multi-million-pound infrastructure project was started then cancelled halfway through at Great expense.

“I’m sure lessons have been learned so that such things will never be repeated.”

A light-hearted calculation suggests that if the 1.2 mile stretch was built again, it could cost more than £300m.

In 2011, the Highways Agency believed a mile of new motorway would cost an average £30 million.

Geoff French, vice president of the Institution of Civil Engineers, told the BBC that as a rule of thumb, an elevated road costs 10 times more than one on the flat.