Improvements to the Thameslink Core between London Blackfriars and Farringdon

Over the summer of 2026, we’ll invest in a programme of works to strengthen the resilience of the vital section of the network between London Blackfriars and Farringdon to prevent future delays

Project timeline

Work will take place over a series of weekends during summer 2026. We will then carry out testing in autumn 2026, with the system planned to be brought into service by the end of 2026.

What work is taking place?

We will improve the train detection systems by installing a dual detection system between London Blackfriars and Farringdon to ensure continuity of services during failures.

Axle counters will be installed alongside the existing track circuits, creating a layered and more robust detection systems. By overlaying axle counters onto the existing equipment, the network will no longer be solely dependent on track circuits, reducing the likelihood of failures impacting services so railway operations will be maintained even if one detection system fails.

This will directly translate into fewer delays, improved punctuality and a more consistent timetable for passengers travelling through one of the busiest parts of the network.

Dual detection has already been installed successfully north of Farringdon in 2020 and delays due to track circuit failures, have been minimal. We expect this trend to be replicated between London Blackfriars and Farringdon, halting the service disruption currently experienced in the event of track circuit failure.

How will this work affect me?

No trains will run through central London between London St Pancras International / Finsbury Park and London Blackfriars / London Bridge.

• On Saturday 13 and Sunday 14 June
• On Saturday 20 and Sunday 21 June (on this weekend there are no trains running between Bedford and London Bridge / Sutton)

To help passengers complete their journeys, paper rail tickets will be accepted at no extra cost on London Underground and London bus services across central London.

Why is the work needed?

The Thameslink Core from St Pancras to Blackfriars is one of the most critical and intensively used sections of the UK rail network, connecting routes from Kent, Sussex, and the East Midlands through central London.

With the high frequency of trains passing through and no diversions possible, any disruption has an immediate and widespread impact on passengers and services. The sheer intensity in the number of services also means that our engineers have limited access for maintenance and rectifying faults.

In recent years, the reliability of our train detection systems has caused significant delays on this section of the network.

Train detection systems are critical to safe, efficient and reliable operations by accurately detecting the presence, location and movement of trains on the tracks. When failures do occur, we must operate under safety-critical conditions which reduces capacity by up to four trains per hour during off-peak periods, leading to congestion and extended journey times.

Recent track circuit failures have caused significant disruption. A failure in November and December 2025 resulted in cancellations and major delays for customers.

The project will help transform resilience, ensuring that even in the event of equipment failure, services can continue running with minimal disruption. This is a key step towards a more dependable and efficient railway for London and the wider network.

Get in touch

If you have any questions, please visit our contact us page or telephone our 24-Hour National Helpline on 03457 11 41 41.