Private equity group Kohlberg Kravis Roberts has agreed the largest Mayfair letting in more than a decade, taking space for its new London headquarters in one of the office developments being built over the new Crossrail stations.

KKR has pre-let four floors at 18-19 Hanover Square on a 15-year lease, according to a statement from Great Portland Estates, a London-listed real estate investment trust that is developing the building in a joint venture with the Hong Kong Monetary Authority.