From nationalrail.co.uk:

Incident created 02/06/2012 19:59 Last updated20:34 - 02/06/2012
Route affected
Stratford, Dalston Kingsland, Camden Road, Gospel Oak, West Hampstead,
Kensal Rise, Willesden Junction, Shepherds Bush, Kensington Olympia,
West Brompton, Imperial Wharf & Clapham Junction / Acton Central,
South Acton, Gunnersbury, Kew Gardens & Richmond
Train operator affected London Overground
Description
Overhead wire problems are causing disruption near Willesden Junction.

Because of this, the following changes will apply until further
notice:
There are currently no trains between Willesden Junction and Clapham
Junction
There are currently no trains between Stratford and Richmond
Journeys may be delayed by up to 60 minutes

Passengers may use London Underground services on all reasonable
routes.


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gordon