As an American, I've always grown up reading about P-51 Mustangs, but never as much about the definitive fighter of the RAF. Was there a fighter that was as predominantly used by the British as the Mustang was for the Americans?
The Supermarine Spitfire. In RAF service from the first day of the war to the last (and beyond), produced in greater numbers than any other British aircraft, firmly embedded in the British psyche both [at the time] (http://www.bbc.co.uk/news/uk-england-35697546) and since, subject of countless books (at least one more due for publication on Thursday). [Why do we love the Spitfire?] (http://www.bbc.co.uk/guides/z3jkwmn) from the BBC gives a very basic quick overview.
The Spitfire's status was cemented in the Battle of Britain. As James Holland puts it in The Battle of Britain: "No other veterans of the Second World War are as hallowed as the Few [Churchill's description of RAF pilots in his famous [tribute] (http://www.bbc.co.uk/learning/schoolradio/subjects/history/ww2clips/speeches/churchill_the_few)], but equally no aircraft is as hallowed as the Spitfire. This aircraft, above all others, has gained an iconic reverence not given to any other. (...) No wonder that generations of children have built models of this beautiful aircraft, or that thousands still flock to air shows every summer to watch them fly." For Stephen Bungay in Most Dangerous Enemy it "plays the mythological role of a magical weapon, the equivalent of [...] Excalibur".
The Spitfire's elevation to mythological status rather blots out more nuanced history (e.g. there were almost twice as many Hawker Hurricane squadrons during the Battle of Britain itself) but if you're after the definitive RAF fighter, there's no competition.