A popular YouTuber, who has visited every railway station in the country, visited Watford to ride a "secret" section of track on the Metropolitan line.

Geoff Marshall, who has sampled the very best of what the British railway has to offer, makes regular videos of himself touring the UK.

He ventures to a wide array of places, ranging from the busiest to the least-used stations, visiting long-lost railways, as well as taking trips to brand new shiny stations.

And he shares all of his experiences with his 235,000 subscribers on YouTube.

One of his most recent trips was to Watford to ride the Metropolitan line's 'North Curve'.

It's a tiny section track that is used just a smattering of times a day - and Geoff had to be up at the crack of dawn to take a ride on it.

Watford Observer: YouTuber and author Geoff Marshall on the 6.08am Rickmansworth to Watford Met Line service which goes via the North Curve. Credit: YouTubeYouTuber and author Geoff Marshall on the 6.08am Rickmansworth to Watford Met Line service which goes via the North Curve. Credit: YouTube

Where is the 'North Curve' and what is it?

So it may not be a complete secret to some commuters and residents in our neck of the woods, but if you've never heard or even knew about the North Curve before, this is it.

It's so hidden, it doesn't actually appear on the official London Underground map.

Watford Observer: The map above is the official Tube map, while the one below is edited showing the 'North Curve'. Credit: Geoff Marshall YouTubeThe map above is the official Tube map, while the one below is edited showing the 'North Curve'. Credit: Geoff Marshall YouTube

The curved track runs between Rickmansworth and Croxley Green via Croxley Hall Woods.

There is a tiny tunnel - the shortest on the Tube network at just 80 metres long.

When do trains ride the North Curve?

Very rarely - it's incredibly under-used. Just three passenger trains use it a day, along with a cluster of empty stock trains in the evening.

You'll have to be up at around 5 or 6am to have a chance to take it.

In his video, Geoff arrived at Rickmansworth station just before 6am to catch the 6.08am to Watford.

For almost every journey on the Met Line, it's impossible to get to Watford Met station from Rickmansworth - and stations west of Rickmansworth - without changing at Moor Park station.

But at 5.16am, a service from Chesham to Watford and at 6.08am, a service from Rickmansworth to Watford takes passengers directly to Croxley and then Watford - by riding the North Curve.

Watford Observer: To the right is the Met Line towards Moor Park, the usual line of journey. But on the 6.08am service towards Watford, the train veered left onto the North Curve. Credit: YouTubeTo the right is the Met Line towards Moor Park, the usual line of journey. But on the 6.08am service towards Watford, the train veered left onto the North Curve. Credit: YouTube

Geoff's 6.08am service was completely empty but as he rode the train, instead of carrying on straight towards Moor Park like almost every single Met line service, the train veered to the left and onto the North Curve.

After going through a tunnel, the curved track rejoins the main Met Line. It took Geoff just four minutes to reach Croxley's station platform from Rickmansworth.

In all truth, Geoff appeared a little underwhelmed by the journey because it was over so quickly - but he had to return that night to ride the North Curve in the opposition direction - from Watford back towards Rickmansworth at 12.49am.

Watford Observer: Geoff Marshall pictured on the 6.08am Rickmansworth to Watford Met line service just as the train enters the tunnel. Credit: YouTubeGeoff Marshall pictured on the 6.08am Rickmansworth to Watford Met line service just as the train enters the tunnel. Credit: YouTube

After experiencing the return journey, Geoff helpfully suggested that those who want to ride the North Curve themselves should do it in the morning when there is daylight rather than during the pitch black.

There's also the chance to catch a glimpse of an empty train riding the North Curve at 5.44am, along with five between 8pm and 9.30pm from Monday to Saturday.

And when there's engineering work on the Met line in the Watford area, trains divert via the North Curve.

Watford Observer: The moment the North Curve line rejoins the main Met Line route towards Croxley and Watford. Credit: YouTubeThe moment the North Curve line rejoins the main Met Line route towards Croxley and Watford. Credit: YouTube

Where can I find the North Curve?

It is possible to view the North Curve track by venturing into Croxley Hall Woods between All Saints Lane and Frankland Road. There's even a sign at the entrance to the woods showing the North Curve.

If you walk into the woods far enough, you'll cross over the regular Met Line track, before eventually reaching a bridge which is actually the tunnel on the North Curve. A peak through bushes and fencing and you'll find the secret track below.

Watford Observer: A map at Croxley Hall Woods showing the North Curve track. Credit: YouTubeA map at Croxley Hall Woods showing the North Curve track. Credit: YouTube

Watford Observer: Geoff Marshall in Croxley Hall Woods on his way to find the North Curve Met Line track. Credit: YouTubeGeoff Marshall in Croxley Hall Woods on his way to find the North Curve Met Line track. Credit: YouTube

Geoff concluded: "It’s awkward to do but it’s fun to do if you’re prepared to get up early or late. That is how to ride the North Curve, the secret bit of track on the Metropolitan line."

Watford Observer: This shows the normal Met Line route towards Amersham. To the right is the North Curve rejoining the main line. Taken from Croxley Hall Woods. Credit: YouTubeThis shows the normal Met Line route towards Amersham. To the right is the North Curve rejoining the main line. Taken from Croxley Hall Woods. Credit: YouTube

Geoff's full video, Riding The Metropolitan Line's Secret Curve Of Track, which has been viewed nearly 100,000 times, can be watched on YouTube here.