Three different train lines have been disrupted because of damage to the overhead electric wires between Shepherd’s Bush and Watford Junction.
Trains running between these stations may be cancelled, delayed or terminated and started back from Shepherd's Bush.
The operators affected are Avanti West Coast, London Northwestern Railway and Southern, with disruption expected until the end of the day.
It comes after emergency services had to respond to reports a person had been struck by a train between Kingston and Teddington.
The incident meant all lines in the area had to be closed, as power had to be shut to allow emergency workers access to the railway, but these have now re-opened and South Western Railway trains are now running as normal.
Meanwhile, there was significant congestion to traffic in central London, with at least one major road closed, after multiple horses bolted through Aldwych.
This has now cleared up, with traffic monitoring site Inrix no longer reporting any resulting congestion.
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Live updates
Serious crash on Upper Richmond Road
The A205 Upper Richmond Road has been closed both ways between Milton Road and Waitrose because of a serious crash.
It has caused heavy congestion to Roehampton Lane back past Barnes Common, and diverting through Mortlake between Barnes Bridge and Chalkers Corner.
This has caused a detour for several buses - number 33, 337 and 493.
London Overground now delayed instead of suspended
There are currently severe delays between Stratford to Richmond and Clapham Junction due to a signal failure at Camden Road.
Earlier, it was suspended between Wandsworth Road and Clapham Junciton (due to an obstruction on track at Clapham Junction).
Good service on the rest of the line.
Lane shut on M25 near Epsom
A lane has been closed on the M25 clockwise - between J8 (Reigate / Redhill) and J9 (Leatherhead / Epsom).
This is for vehicle recovery.
Traffic-monitoring site Inrix is showing congestion in the area but nothing severe yet.
M25 near Enfield no longer delayed
We told you earlier about two-mile tailbacks - from J24 A111 Stagg Hill (Potters Bar) to J23 A1M (South Mimms) - caused by a stalled lorry.
Lanes had re-opened before 10am but disruption was still in place for a little under an hour.
This is no longer the case, with Inrix reporting clear roads.
Severe delays to London Overground
There are currently severe delays between Stratford to Richmond and Clapham Junction due to a signal failure at Camden Road - good service on the rest of the line.
Northern line no longer delayed
The Northern line has returned to running a good service.
Buckingham Palace Road no longer closed but traffic still delayed
We told you earlier about how Buckingham Palace Road was closed amid the chaos caused by horses bolting through central London.
The road has seemingly re-opened, according to traffic monitoring site Inrix, but there is still a lot of congestion to roads in the area.
Minor delays to Northern line
There are currently minor delays between High Barnet and Camden Town southbound only due to train cancellations - good service on the rest of the line.
Trains to Alexandra Palace delayed
Great Northern trains between Potters Bar and Alexandra Palace are currently disrupted because of a points failure.
Trains could be delayed or cancelled until at lest 11am.
London Waterloo train disruption expected until the end of the day now
Multple South Western Railway trains are delayed and cancelled after reports a person being struck by a train between Kingston and Teddington earlier this morning.
The disruption caused by this was expected to last until 10am but National Rail has now said it will likely be the case for the rest of the day.