Simmons & Simmons received £15.5m in fees from the Ministry of Defence (MoD) between 2002 and 2005 before it was sensationally dumped from the defence department's legal panel in January.
The firm is now facing an annual cash black hole of more than £3m following the MoD's review that cut Simmons, citing a poor pitch to meet the MoD's future needs.
Figures provided to The Lawyer through the Freedom of Information Act reveal Simmons received £15.5m in fees from the MoD between 1 May 2002 and 30 September 2005. The firm had relied on the MoD for more than £3m in annual fees, with the figure spiking in 2002-03, when Simmons received £7.3m Freshfields Bruckhaus Deringer is set to be the main beneficiary of Simmons' departure, having seen its fees increase from less than £3.5m between 1 May 2002 and 30 April 2004, to nearly £4.5m in 2004-05.
At the midpoint of the current financial year, Freshfields had already received nearly £2.5m from the MoD.
It is the second time Simmons has found itself facing a gaping chasm in its accounts, after it also lost Railtrack as a major client in 2002.
Simmons saw its fees from the MoD spike in 2002-03 on the back of the first stage of privatisation of QinetiQ, in a deal which saw Clifford Chance client Carlyle Group buy a 31 per cent stake in the defence research agency.
Simmons continues to advise the MoD on the Future Strategic Tanker Aircraft project, a £13bn air-to-air refuelling project and the MoD's largest current project. It is also advising on the Military Flying Training System and the Defence Training Rationalising projects.