M25 shut anticlockwise at junction 15 near Heathrow until 10am on two October Sundays

National Highways will close the M25 anticlockwise through junction 15, where it meets the M4, on two weekends this month. Each closure starts at 8pm on a Saturday and lasts until 10am on the Sunday, which affects drivers heading to Heathrow.

The first closure is from 8pm on Saturday 17 October to 10am on Sunday 18 October. The second starts at 8pm on Saturday 24 October and ends at 10am on Sunday 25 October. The closed section lies between the M4 slip roads.

M25 junction 15 closure: what stays open

The clockwise carriageway is not affected, and every link between the M25 and the M4 stays open. Only traffic going anticlockwise through the junction is stopped.

National Highways expects the interchange to be at its busiest between 8am and midday on both Sundays. It also warns that some delays could continue after the road reopens at 10am.

Diversion route and Heathrow terminals

Drivers carrying on anticlockwise will be signed onto the M4 heading west as far as junction 5. There they come back the other way along the M4 and rejoin the M25 anticlockwise at junction 4b. Drivers are asked to stick to the signed route and not change plans at the last minute. Anyone unsure of the way should hand the checking to a passenger or pull over somewhere safe first.

According to Heathrow’s own driving directions, traffic for Terminals 2 and 3 uses the M4 and passes through the junction 15 area. Terminals 4 and 5 can be reached from junction 14 of the M25. Travellers are advised to look up the route for their own terminal rather than just entering ‘Heathrow’ into a sat-nav.

The 10am reopening is a problem for late-morning flights. A passenger on a midday flight who wants to reach the terminal three hours early has to be there by 9am, an hour before the road reopens.

British Summer Time also ends on the second weekend. At 2am on Sunday 25 October the clocks move back an hour. Anyone who has booked an overnight collection or an early transfer should confirm both the day and the time with whoever is driving them.