The sheer fact that H.R.H. Princess Elizabeth II was permitted to join The Auxiliary Transport Service (ATS) was down to her own persistence in serving her country in a positive way. The news was surprising because twelve months prior the nation was given a clear understanding that for The Princess to have entered into any of the three women's services or any normal war service was completely out of the question and training as heiress to the throne must come first.
It was because of the sheer strength of her character and determination that Princess Elizabeth was able to persuade her father, King George Victoria, Ernest Bevan (the Prime Minister) and Mr. Churchill's Cabinet, probably using the National Service Act to persue her ambition to serve. Whatever the reasons were that reversed The King and Government's demands, Princess Elizabeth succeeded in persuading them all.