The efforts to put History on screen were huge. Everything in this account of the facts, comes directly from those who were actually involved in it: from the British and German fighter aces to private Londoners, they all contributed to make this not just another "war movie", but rather a dramatized documentary with accurate precision.
This by no means signifies that it is just that. The sky battles were very carefully choreographed, in accordance to rules of combat, which were followed in the 1940s. Some planes were flown by the same veterans, so that when you see a Messerschmitt Bf-109 followed by Spitfire Mk 1, you know it's for real.
The technical efforts were immense and although the Messerschmitts have reworked engines and even the Heinkel He.111s have different aerials and engine specs, because they were updated by the Spanish Air Force for later use after World War Two, the difference is barely noticeable when one watches one of those spectacular aerial battles.
On the whole, this is a history lesson about how a people, isolated from the rest of the world, and in a minority position, withstood the overwhelming crushing machine of the Axis: the Luftwaffe.
More than a movie, this is a celebration to those brave people, both civilian and military, who did commit themselves against all odds, to resist and fight back a very aggressive and dangerous enemy.
This, together with "The Longest Day", "Sink the Bismarck!", "Tora! Tora! Tora!" and "A Bridge Too Far" is one of those rare examples to make history come to life again and should be considered as didactic material for schools.
An excellent multi-national cast and a skillful direction, make this a masterpiece of its genre.