It was discovered, after the information became declassified, that a military rocket trajectory computer was accidentally delivered to the then EMI studios (which became Abbey Road) in late August 1962.
George Martin had ordered a bespoke sound mixing desk to be installed in Recording Room 2 the moment Brian Epstein had negotiated the Beatles' release from their contract with Bert Kaempfert in the early summer of '62.
The desk was to be largely made by legendary sound stage engineers Harrison in Nashville then shipped to Boeing in Seattle, who had made a bespoke chassis for the mixer and would also be handling its delivery to the United Kingdom. However, Epstein's brother who held a senior position at the avionics company wanted to covertly test a new audio passthrough device which Boeing believed would have superior static negating qualities in consumer audio.
Deciding that Brian (and George, who he knew vaguely) would be sworn to secrecy he had his engineers install the static reduction system (the original intention was to improve pilot to radio tower audio which had not progressed a great deal since the war) in the desk.
When it was due to be wrapped and shipped in July of that year, a rocket trajectory computer was on the same carnet - due to be delivered to RAF Halton, 30 miles away from EMI studios. Because both the machines looked incredibly similar - having been manufactured next to each other using the same materials and processes and were the same size, the factory manager simply labelled the two desks as SPDK1 and SPDK2 (Special package / Don't know), presumably not wanting to ask too many questions. They were then sent to the UK via Newark with the mixing desk delivered to the RAF and the trajectory computer ending up in north London.
Because both devices were so complicated and alien to the engineers at both locations, it wasn't until a month later that George Martin realised that he wasn't getting any audio from his missile guidance system and the RAF couldn't control missiles with cross faders and treble boosts.
Realising Boeing's mistake, the MOD had the devices swapped overnight and in great secrecy (note the speed, given both machines needed 19 days to be installed in the first instance) , 2 weeks before Please Please me began its recording sessions.
The static reducer never worked, due to dead capacitors on its logic board.