For an hour after dawn on 13 August, there were few German tracks upon the plot tables in operations rooms, and none at all in the central and eastern Channel. The first signs of concentration, however, came earlier than usual, for between 05:30 and 05:40 two formations of 30 or more aircraft were located in the Amiens area. For 30 minutes, they remained over land, but at 06:10 they began moving inland. The Observer Corps and radar tracked them and guided the RAF units to intercept. Unaware of the German intent, the controllers directed three full Squadrons and detachments of three others were alerted by 06:15. No. 151 was protecting a convoy in the Thames, No. 111 was protecting RAF Hawkinge and No. 74 Squadron RAF was covering RAF Manston. Parts of No. 85, No. 43 and No. 238 Squadron RAF were also airborne near London. By 06:25, the German formations were well over the Channel. No. 238 was moved to cover their own base at RAF Warmwell. No. 257 Squadron RAF was also ordered to take off at 06:20 to patrol Canterbury. Not satisfied with the strength of the forces already airborne, controllers dispatched No. 601, 213, 64 and 87 Squadrons to intercept between 06:30 and 06:35. The first combats began at 06:30.