Secrets of The Motorway - M25 Part 3

Summary

This video details the journey of the final episode of 'Secrets of the Motorway' series, which explores interesting facts and history about each junction along the M25 motorway in England. It starts at Junction 21, giving background on the missing slip roads, and continues clockwise, covering things like the old Radlett Aerodrome, the failed London Ringways project explaining the odd road layouts, tunnels like the longest Homesdale Tunnel, the heritage railway line near Epping, the origins of the Brook Street Interchange, and finally ending at the Mardyke Interchange, the last junction on the M25.

Takeaways

• 😀 This is the last episode of a series exploring the secrets of UK motorways that started in July 2022
• 🚗 The M25 passes through the former site of Radlett Aerodrome, an airfield from 1929 that had a grass runway
• 🚥 Junction 23 of the M25 has lots of traffic lights, making it slow to get around the junction
• 🚧 Between junctions 19-23, the M25 was pieced together from failed London ringway projects originally not meant to connect
• 🚇 An underground central line tunnel crosses under the M25 near junction 27 in Essex
• 🌉 The longest M25 tunnel is the Huntsdale tunnel in Waltham Cross, built with the cut and cover method
• 🎡 Old McDonald's Farm next to junctions 27-28 is a landmark that almost wasn't there based on old motorway plans
• ⛰ The junction 28 Brook Street Interchange was built over the River Mardyke, necessitating dedicated slip road bridges
• 🛣 Before the M25, the A127 crossed straight through junction 29, remnants of which can still be seen today
• 😊 The host John thanks viewers for their support over 80 episodes documenting UK motorways

Q & A

What is the name and topic of the video series?

The name of the video series is 'Secrets of the Motorway'. It explores different motorways in England, Scotland, and Wales.

Why are there missing slip roads at Junction 21 of the M25?

The missing slip roads likely weren't built because they wouldn't have fit at the existing Junction 6 of the M1 which was constructed before the M25. Installing them would have caused issues.

What was on the site where the M25 now passes between Junctions 21 and 22?

The site was previously Radlett Aerodrome, an airfield that opened in 1929 and was home to aircraft manufacturer Handley Page. The M25 passes between where the main runway and some buildings were located.

Why do the M25 carriageways split at Junction 23?

That section was meant to be part of the failed London Ringways project as Ringway 3 and Ringway 4. When the project was cancelled, existing sections were joined, causing the odd layout.

What is inside the large bridge near Junction 25 of the M25?

Inside the bridge is the New River, an artificial waterway built in 1613 that carries drinking water into London. The bridge was built so the river wouldn't be disrupted.

Where is the longest tunnel on the M25 located?

The longest M25 tunnel is the Huntsdale Tunnel in Watford Cross, built using the cut and cover method in the 1980s.

How does the Central line relate to Junction 27 of the M25?

The Central line railway runs underneath the M25 near Junction 27. Trains used to run as far as Ongar station until it closed in 1994.

What could have been at the Old McDonald's Farm site near Junction 28?

Ringway 4 was planned to connect with Ringway 3 at that site via an interchange. The farm may not have existed if those plans went ahead.

How did construction of the M25 impact the A127 at Junction 29?

The A127 had to be shifted over to make way for the M25 and junction. Remains of the old A127 carriageway can still be seen.

Why do the southern slip roads at Junction 30 have their own bridges?

They cross over the Mardyke River, so separate bridges were built. This also allows emergency vehicle access between carriageways.