Greater London's Metropolitan Police Service (MPS) has extended its contract with IT services supplier Capgemini until December 2015.
The original £350m seven-year deal was signed in 2005, but the police service opted for an early renewal.
The extended contract will lock agreed cost savings in place and help management set budgets with greater certainty, the MPS said in a statement.
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The contract is expected to provide £43m in savings when supporting London's 55,000 police and community support officers and staff.
The cost saving will come from increased automation, improved processes, rationalisation of services, closer collaboration and simplified reporting, said Capgemini.
The services company manages and supports desktop IT networks, telephony and mobile devices, for the MPS, which includes about 30,000 desktops and laptops, 38,000 telephone extensions and 8,500 mobile phones.
Capgemini, which earlier this month lost out on a deal with the Cleveland Police Authority said the MPS deal will help plan the resources required.