Train services will be disrupted on a number of routes around London today, because of leaves falling on rail tracks.
Southeastern rail will run a revised timetable because of high leaf fall.
National Rail said: "On days or weeks when leaf-fall is at its highest and rails are most slippery, train operators will need to introduce a different timetable on some routes. This is to make sure you are where you need to be with the minimum of delay.
"Conditions today are expected to be particularly challenging and Southeastern will be running a revised timetable throughout the day, particularly during off-peak periods."
Gatwick Express timetable changes
Meanwhile, Gatwick Express warned today that it will make leaf fall-related timetable changes effective from Monday, 16 October, running until Friday, 8 December.
"In line with the rest of the industry, Gatwick Express is taking steps to manage the effect of the leaf fall season rail conditions on passenger services," the rail operator said.
"The changes... will help to reduce congestion and reactionary delays to Gatwick Express and other services on the Brighton mainline."
Last year, London commuters faced huge disruption on the Piccadilly Tube line, caused partly by leaves causing the tracks to become slippery. This year, Transport for London is planning to tackle the problem by spraying glue on the tracks.
Heathrow Connect problems
National Rail said this morning that, due to a large number of trains requiring urgent repairs, there will be no Heathrow Connect service between Paddington and Heathrow Airport today.