FirstGBRf held a major event at their new Wellingborough depot on 12 June 2007, to mark the official opening. The facility, on the site of the former Finedon Road sidings, north of Wellingborough station will be used to stable, load and form up material trains for the FirstGBRf/Metronet London Underground relaying contract. The official opening was performed jointly by FirstGBRf Managing Director John Smith, and Mark Thurston, Deputy Chief Programmes Officer for Metronet.

The Wellingborough facility is the only one of its kind in the UK, it allows the Rail and Sleeper Delivery Train (RSDT) to be stabled and loaded with raw materials, using the very latest in train loading equipment, consisting of train mounted cranes to load rail, and depot gantry cranes to load sleepers. The rail is sourced from the Corus Scunthorpe plant and shipped in 216m lengths to Wellingborough. Sleepers are made at the RMC plant at Washwood Heath, Birmingham.

The Wellingborough facility was funded by Metronet Rail, to reduce the risk of on time train deliveries for weekend engineering possessions. FirstGBRf run trains of up to 400m in length of rail, sleepers and ballast, powered by Class 66/7 locos, direct to London Underground worksites.

FirstGBRf has a 10 year £80m contract with Metronet which started in 2005, since then some 84km of new track has been laid, with each work block allowing twice as much relaying to be done than using the previous methods.

FirstGBRf trains are operated on the main lines by GBRf train managers, but within work sites some Metronet staff have been trained on their operation. In mid 2007, the progression of work was on the northern section of the Metropolitan Line.

All wagons used for the project are painted in Metronet yellow and are joint registered for Network Rail and LUL use.

The sizeable site at Wellingborough has space for major expansion and FirstGBRf are hopeful to redevelop spare capacity for other uses, possible intermodal freight. The site is directly connected to the Midland Main Line.