The M25 turns 40 on 29 October, with new research revealing that journeys on one particular stretch take more than three times as long at the afternoon peak as later in the evening.

Vehicle data company Geotab found that all eight of the most congested stretches were between junctions 10 and 20, around the M3, M4 and M40 interchanges, particularly near London’s Heathrow airport .

The clockwise journey from junction 14 to junction 15, towards the M4, averaged 9.2 minutes at 4pm, compared with three minutes at 7pm. Further north, travelling anticlockwise from Mill End towards Denham, between junctions 17 and 16, took 15.6 minutes at 7am and 6.6 minutes at 7pm.

The western section of the M25 is the busiest with peak-time journeys taking three times as long as in the evening (PA)

The analysis covered 12 sample weeks between September 2025 and August 2026, across 46 of the 58 sections, counting each direction separately.…