Office construction is up 28% over the past six months, and 51 new projects have started, the highest ever recorded by Deloitte’s annual office development survey.

London now offers 14.2M SF of office space, the highest level since the first quarter of 2008. This is good news for tenants who have greater choice—and bad news for landlords who will need to start making concessions to keep desirable tenants.

The construction boom is changing Midtown more than any other submarket with a 58% jump in development. There are nine projects under construction, adding 1.2M SF. The busiest locales are closest to the new Crossrail stations near Tottenham Court Road and Farringdon.

The crown jewel of Midtown is the nine-story, 843k SF trophy that Golden Sachs is building at 70 Farringdon St.

42% of space under construction is now let, up from 38% six months ago. Financial services are gobbling up most of it; international banks have committed to over 1.5M SF, 25% of all let space.