We're already getting there. Last week, British Land said it was letting space at more than euro 74.57 ($95.43) per square foot for the first time in five years. Now JLL reports prime city office rents are some of the highest in the world at about euro 80.52 ($103.04) per foot. Prime West End office space in London hovers at euro 86.46 ($110.65).

"Prices are being driven up by the return in demand by financial-services firms across the board," says Neil Prime, Jones Lang Lasalle's head of office agency. "It is simple economics of more demand and less supply. However, there will be a lag in new space becoming available. We look set to see selective shortages in some areas of the market, driving rents up sharply."

Property researchers estimate that between now and 2009 almost six million sf of newly developed office space will become available. Big projects include British Land's developments at 201 Bishopsgate and the Broadgate Tower, Land Securities' scheme at three Bankside and Hammerson's redevelopment of the former London Stock Exchange at 125 Old Broad St.