But Chief Executive Nigel Kempner told GlobeSt.com that the outlook was now very uncertain. 'It has become almost impossible to forecast events after 11 September,' he said. 'Short term one has to be cautious, but the underlying factors in the West End market remain strong.'

Kempner said that Benchmark would continue to focus on the prime West End districts of Mayfair, St James's and Kensington. Historically these areas have been more resilient during economic downturns than other London locations like the City. 'Not one sector accounts for more than 18% of the West End economic base,' he said.

And he said that Benchmark had little exposure to space let at the top of the market which is possibly now over-rented. 'Only a handful of buildings in the West End ever hit £85 ($124) per sf,' he said. 'And across our two million-sf portfolio the average rent passing is just £30 ($44) per sf with an ERV of about £40 ($58) per sf.'