It comes after the company – which runs the Docklands Light Railway, the Boris Bikes scheme and the Atomic Weapons Establishment – was accused by the Government, one of Serco's biggest customers, of overcharging taxpayers to monitor the electronic tags of offenders who were actually dead, non-existent or in custody. Serco is also facing a separate police fraud investigation over alleged misreporting in a £285m prison escorting contract, amid claims staff recorded prisoners in London and East Anglia had been delivered ready for court – a key performance measure on the contract – when in fact they were not.