Police are advising drivers to avoid the M25 until mid-afternoon after a lorry fire closed the carriageway on both directions in Hertfordshire.
The section between junctions 21a and 23 near the South Mimms services is expected to be closed until 3pm.
Long tailbacks have built up on surrounding roads.
More top news
Ukip has responded to the resignation of its only MP, Douglas Carswell, by suggesting he quit before he was kicked out.
A mostly warm afternoon but a fresh easterly breeze will bring a noticeably cooler feel along eastern coasts. Highs of 15 deg C (59 deg F).
ITV News Anglia's Political Correspondent Emma Hutchinson asks what next for UKIP after Douglas Carswell quits the party?