text: The Class 313s operated Metro services on the electrified routes; they were joined on the Euston - Watford Junction service in 2003 by three Class 508s transferred from Merseyrail. The Class 321s operated County services to Northampton and Birmingham; they were joined in 2005 by new Class 350s. The Watford Junction - St Albans Abbey service was operated for many years by Class 313s, but later was usually operated by Class 321s with Silverlink Metro drivers and Silverlink County guards.
  On 16 July 2004, Virgin Trains announced that it was withdrawing most of its stops at Milton Keynes Central, which were used by up to 6,000 passengers a day. Commuters became unhappy at the prospect of switching to older Silverlink trains, and a longer journey. Silverlink countered this with the temporary usage of ex-Virgin stock, still in Virgin colours.
  The Strategic Rail Authority decided to divert thirty four-carriage Siemens Desiro trains from an order placed by South West Trains to provide stock with faster acceleration for the West Coast Main Line operators. These trains, the Class 350s, were not allocated to a specific operator, but were instead used jointly by Silverlink and Central Trains, both owned by National Express.
  Pending the arrival of these trains, from September 2004 Silverlink introduced two sets of Mark 3 carriages, formerly of Virgin Trains, hauled by Virgin Class 87 and EWS Class 90 electric locomotives on peak-hour Northampton services. Additionally, five Class 321s were hired from One, another National Express-owned operator.
  Fleet