AS FAR AS I KNOW - ER.103 was NOT issued in 1947. The 100-series specifications began in 1950 and Experimental Research Specification 103 was issued that year. Also, it was NEVER part of the EE P.1 story - ER.103 was issued purely to cover the Fairey Delta II. The P.1 was always covered by F.23/49 and if you go into the National Archives at Kew you will find documents with Air Staff folk still calling it the F.23, even in the late 1950s after the name Lightning had been allocated to the P.1B.
The P.1 and what became the FD.2 started life in 1948 after The Advanced Fighter Project Group had been formed at RAE early that year. Armstrong Whitworth, Boulton Paul, English Electric, Fairey, Gloster and Hawker submitted designs to an unofficial requirement/specification/letter for a research aircraft. The AW.58 design was ordered and specification E.16/49 written around it, but it was later cancelled. The P.1 was ordered as a fighter prototype to F.23/49, and what became the FD.2 was covered by ER.103 shortly afterwards. In fact ER.103 was initially called ER.100D, but that number was allocated to the Shorts SB.5.
ER.103 is dated 26th September 1950. I have never seen any records that ER.103 appeared in 1947, but if someone can show hard evidence to prove that it did, I will gladly take these comments back.
