Germans who claimed to be catching butterflies in pre-war Kenya caught the attention of British officials who feared the Nazis were plotting to invade East Africa, previously secret files reveal.
UK colonial administrators paid close attention to the activities of Germans, Italians and the Japanese in the region in the years before the Second World War, recording shipping movements and even safari trips in intelligence reports.
Two German men found camping in Kenya's Rabai Forest in August 1938 - one a suspected Nazi agent and the other a Palestinian of German descent - told British officials they were engaged in butterfly-catching.
They claimed they had been recommended to go there by a well-known naturalist, but it turned out that he did not know them.
Another report from October 1938 records that members of the Wataita tribe had for several months observed Europeans of an unknown nationality regularly climbing to the top of a hill "to admire the trees".
The file notes: "No evidence of hidden arms, stores or a likely 'hide out' was found, although it was stated that the Kisigau Hill would make an ideal strategic retreat."
The records, released at The National Archives in Kew, west London, demonstrate British fears about Nazi plans in the lead-up to the outbreak of war in September 1939.
A monthly intelligence report from the Kenyan port of Mombasa in August 1938 observes that a German called Herr Stieglitz, a representative of German tyre manufacturer Continental, had recently been on two safaris, on one of which he killed a buffalo.
It continues: "Contact remarked that he would not like to be within range of a rifle in the hands of this person, whom he described as being a 'crack shot'. He also stated that the Germans who visit Kisigau usually shoot something."
The same document records that a drunken Italian ship's officer told a source he had heard Germans say they could organise a "semi-trained force of about 5,000 men" in East Africa if hostilities broke out.
Another report from November 1938 says that up to 2,000 Germans have been seen building roads, assembling lorries and trading in neighbouring Italian Somaliland, present-day Somalia.
They carried no weapons and most wore "khaki safari coats and shorts", but they apparently included two Luftwaffe officers who were observed in full uniform with Nazi swastika armbands at a parade to celebrate the birthday of Italian king Victor Emmanuel.
British officials were highly sensitive to the danger of inflaming tensions with Germans in Africa, the files show.
A man called GW Ockenden caused a scene on board a German ship docked at Mombasa in December 1938 by wrenching a photograph of Hitler from the wall of the first class lounge.
UK port police and magistrates took the matter extremely seriously, and Mr Ockenden received the maximum possible fine of 200 shillings.