I came across these N12 photos in a 1946 edition of 'Dinghy & Small Craft racing by T Norman Hinton published by H F Witherby Ltd. The chaos of start lines does not change.
Look at the size of the ensign of the boat on the first picture. It looks like it has come from a Battleship!
You couldn't miss that start line flag 8) Looks to be a blue ensign as it is so dark (though poss red), could be from the local yacht club