Work to deliver a 25 per cent capacity increase on the London Overground network will begin in October.
It will mean a partial suspension of the Bakerloo line and some London Overground services connecting to Willesden Junction for a five day period.
The platform extension work is part of Transport for London's (TfL) continuous programme of investment and delivery of passenger benefits to London Overground and will enable its trains to be lengthened to five carriages.
The extension works will take place at Willesden Junction between 29 October and 2 November.
TfL's Director of London Overground, Mike Stubbs said:
'I apologise for the inconvenience caused but these works are essential for the high-performing London Overground service to continue to grow to meet increasing demand. Before we can deliver to passengers a fifth carriage and the benefits of extra space and a more comfortable commute, we need to extend not only the platform at Willesden Junction low level station but also carry out some track work there.
'To help reduce disruption, we have scheduled the work for the mid-term break which always sees reduced numbers of passengers.'
Because the works involve Willesden Junction's Platform 2, Bakerloo Tube line services which use the low level part of the station are also affected.
The works are part of a £320m, 25 per cent capacity increase programme across the London Overground network.
To accommodate the longer trains, station platforms across the network are being extended, train depots upgraded and expanded, new train stabling facilities built and alterations made to the signalling system.
London Overground achieved one of the UK's highest scores for passenger satisfaction (91 per cent compared to a national average of 82 per cent) in the results of a survey published last month by independent transport watchdog, Passenger Focus.
The railway also came in at number two in Network Rail's performance and punctuality tables for the past year to June 2014 with 96.1 per cent of its trains reaching their terminating station within five minutes of their scheduled arrival time.
This compares with the national average of 89.7 per cent.
Notes to Editors