Drivers heading to Heathrow this month are being told to double‑check their journey times after National Highways confirmed two “overnight” M25 closures that run until 10am on Sunday mornings. potentially disrupting late‑morning and even lunchtime flights.
Closure dates and times
National Highways has confirmed the M25 anticlockwise carriageway at junction 15 (the M25/M4 interchange, between the M4 slip roads) will be closed during these periods:
- Saturday 17 October 2026, 8pm – Sunday 18 October 2026, 10am
- Saturday 24 October 2026, 8pm – Sunday 25 October 2026, 10am
The clockwise carriageway and all M25–M4 connections will remain open, but the anticlockwise route through junction 15, a key approach for many Heathrow-bound drivers will be shut.
National Highways expects the interchange to be busiest between 8am and midday on those Sundays, with some residual delays possible even after the 10am reopening.
Why “overnight” still affects daytime flights
Majid Ismailzada, Marketing Director at GM Rides, warns that the word “overnight” can mislead travellers into thinking the work will be finished before they set off.
“The important question is what time you will reach that section of motorway,” he says, urging passengers to plan around their terminal arrival time, not just their flight time.
A noon flight with a three‑hour airport arrival window means being at the terminal by 9am before allowing for the drive itself, parking transfers or potential congestion.
“Once you work backwards from check‑in, security and the time needed to reach your terminal, your journey may fall much earlier than you first think,” Ismailzada adds.
Heathrow’s own driving directions route Terminals 2 and 3 via the M4 and the junction 15 area, while Terminals 4 and 5 can be accessed via M25 junction 14.
Travellers are therefore advised to check the exact route for their terminal rather than simply entering “Heathrow” into sat‑nav systems.
Official diversion route
For traffic continuing anticlockwise through the closed section, the signed diversion is:
M25 anticlockwise → M4 westbound to junction 5
Turn back eastbound on the M4
Rejoin M25 anticlockwise at junction 4b
Drivers are being told to follow the signed route and avoid last‑minute changes while driving; if directions need checking, a passenger should help or the driver should stop somewhere safe.
Clocks go back on 25 October
The second closure weekend coincides with the end of British Summer Time. Clocks go back one hour at 2am on Sunday 25 October, so anyone arranging an overnight collection or early‑morning transfer should confirm the date and local time with their driver.
