Fifth Floor, the in-house restaurant of the Harvey Nichols department store in London, will close next month for four months while a £1m overhaul is carried out.
Full-year results unveiled last week showed Harvey Nichols's stores and restaurants, which include Prism and the Oxo Tower, both in London, were badly hit by the collapse in the capital's tourist trade following 11 September.
The 135-seat Oxo Tower saw sales fall by 1% and those at the 120-seat Prism were down by 11.8%.
Combined sales for the standalone restaurants came in at £12.3m, compared with £12.6m in 2001, with operating profits falling to £1.1m, against £1.2m last time round.
The Knightsbridge Fifth Floor saw its sales decline by 5.6% for the same reason, but the Leeds restaurant reported sales up by 13.7%.
Group commercial director Patrick Hanly said that sales at Prism and Oxo Tower had fallen by some 15% between September and November. While Oxo Tower had recovered rapidly, Prism was taking longer, he added.
"Collectively," he said, "the restaurants have been 2% up for the past nine weeks. We have gone from quite a low, but Oxo Tower is now enjoying quite nice trading.
"It is easy to forget how concerned everyone was in October and November."
Prism's private dining rooms would now be marketed aggressively to try to bring in more evening diners, while the lucrative wedding market offered an opportunity to bring in weekend trade, he suggested.
As a whole, in the year to the end of March, pre-tax profits at Harvey Nichols fell to £12.5m, compared with £15.6m the year before.
Two new department stores, opening in Edinburgh in September and Manchester next year, will both have Fifth Floor-style restaurants.
by Nic Paton