Leigh-Mallory controlled the air battle from 11 Group headquarters at RAF Uxbridge; commands flowing through the system as normal to Sector control rooms and from there to the airfields. An RAF officer from Hut 3 at Bletchley Park was seconded to the 11 Group Operations Room to filter material to the Y-stations at RAF Cheadle and RAF Kingsdown which intercepted Wireless telegraphy (W/T) and Radio telephony (R/T) transmissions and used direction finding to pinpoint the origin of the signals. The intention was to reduce the time to pass decryptions of material from German radar, observer posts and fighter control to 11 Group through "the most expert officer in Y on German Fighter Defence and its ramifications". The Fighter Controllers on the Headquarters ship and could communicate with the raid fighter cover on a shared frequency. The "Close Support" fighters checked in with the headquarters ship as they approached so the Fighter Controller could direct them onto alternative targets as required.