the aintree iron is said to be the famous Aintree racecourse outside of liverpool,viewed from the air it is shaped like a flat iron, hence the name "aintree iron"
I think that if there is a definative, it is in Mike McGears head
and not really debatable. He says so in the link above.
However, and I may be wrong, I thought he gave an interview in the late 80's early 90's when he said that Tommy Smith the Liverpool footballer was the "Aintree Iron"
given he was a renowned very hard man at a time, when the league was packed with hard men.
I too remember the interview where Mike McGears stated that Tommy Smith of Liverpool FC was the Aintree Iron, and, incidently, Tommy Smith has recently released a biography entitled " Anfield Iron"
Hamish