Jill Bartlett has won a five-year £1m extension with Shearman & Sterling - the contract caterer's first ever client.
The deal with the City law firm launched the company onto the contract catering scene in March 2004.
The extended deal will see Jill Bartlett continue to provide café and corporate hospitality services to the London law firm until 2013. Stern Consultancy handled the tender, which went to a shortlist of four.
Malcolm Banks, premises manager at Shearman & Sterling, said: "In today's economic climate, it was important for us to safeguard our catering offer for the next five years.
"Our decision to re-appoint Jill Bartlett & Company was based not only on its outstanding catering to date, but also its commitment to providing what we need at a competitive price."
Company founder Jill Bartlett said the team was "terribly proud" to have retained the contract, which held a special emotional attachment as its first.
The extension comes a month after the caterer won a deal to cater for staff at Guardian News and Media's new headquarters in Kings Cross, north London.
By Chris Druce
E-mail your comments to Chris Druce here.