and end of messages. SOE London paid no attention. The messages that Lauwers transmitted as a prisoner of the Germans included requests that additional agents and supplies be sent to the Netherlands. SOE responded positively. Agents and supplies, including weapons, were usually flown out of Britain at night and dropped by parachute from converted Handley Page Halifax bombers or landed in fields by Westland Lysander STOL aircraft. SOE air operations were based at RAF Tempsford. The agents and supplies were met on arrival and captured by the Germans. Playing England Several captured Dutch radio operators continued broadcasting encrypted messages but without security checks, which should have alerted SOE that they had been compromised. SOE's head of codes Leo Marks later claimed to have realised that unlike all other coded messages from agents in other countries, the Dutch messages contained no errors. He reasoned that was because they were coded not in the field by harried and harassed wireless operators but by expert German cryptographers. The Dutch messages were too good to be genuine. In the documentary Churchill's Secret Army, Marks recounts how a wireless operator ended a telegraphic radio communication with "HH", which stood for Heil Hitler and was the usual closing for German communications. The other party instantly replied "HH", which indicated that the transmitter was a German who was used to adding "HH" to messages automatically and not a British agent, who would have been confused by the two letters. Finally, Marks sent a Dutch agent in the Netherlands a deliberately garbled message. Marks reasoned that no ordinary SOE agent could decrypt the message, but the German cryptographers would. The Dutch agent responded to the garbled message, which indicated to Marks that he was transmitting under the control of the Germans. Marks reported the findings to his superior, who told him to not discuss the matter with anybody else; no action was taken. German wireless operators reported mock resistance groups and sabotage successes to SOE London. When SOE London requested for an agent return to England, he would suddenly meet with a calamity of some sort and so he could not return. In January 1943, Marks wrote a report to SOE leaders about his suspicions that all or nearly all SOE agents in the Netherlands were in German hands, but it was months before any action was taken. Neither the Dutch section, overseeing operations in the Netherlands nor