Piccadilly line upgrade ‘to blow £3bn budget’ as passengers told not to expect new trains for a year

• TfL expects to exceed the £2.994bn budget for the Piccadilly line upgrade due to substantial and rising costs, particularly for modernising the ageing Northfields and Cockfosters depots

• The first of the 94 new air-conditioned, walk-through Piccadilly line trains is unlikely to enter service until late 2025, up to a year later than hoped

• To save money, TfL plans to “life-extend” the severely aged Northfields depot for up to 15 years instead of rebuilding it—though officials warn this may not offer good value—while fully upgrading Cockfosters depot as originally planned