Oberfähnrich Meyer had been a Bordfunker with 1.(F)/122 until his Me 410 came down off the British coast and he was taken prisoner on 26 April 1944. In captivity, he told a pilot from 5./KG 2 about things he had seen in France. He also told it to microphones concealed by the Combined Services Detailed Interrogation Centre (CSDIC) on 6 May:
A ‘109’. was being modified on an airfield near ours, It was just about ready. It was being specially modified for high altitudes; it was supposed to reach a height, of 13500 m., so the wings were fitted with mid-sections … quite considerably longer wings …
In his formal interrogation, Meyer is reported as saying that:
… a high altitude Me 109 with a wider wing than is normal was about to be put into operation [which] would attain a height of 13,500 metres.
On 10 May, the Technical Officer of FAG 123 signalled Oblt. Kaiser of the 5. Staffel to collect a Bf 109 G-5 “with H installation” («H-Einbau») from the workshops at Guyancourt, south west of Paris. By the 16th, the 5.(F)/123 was able to report the taking over a Bf 109 H “converted from G-5.” The reaction of Air Ministry Intelligence to this was “no definite information about Me 109 H but probably for high altitude PR.”