Princess Elizabeth In The ATS

Princess Elizabeth, the heiress presumptive to the English throne, is undergoing training in vehicle mechanics, learning about tires and carburetors. She is treated like any other trainee and is visited by her family, where she demonstrates her knowledge of fan belts and spark plugs. Her father has given her an officer's commission, making her the first woman in the royal family to join the service full-time. Despite her limited experience with public transport, she now drives a truck for the Red Cross, showcasing her commitment to service.

In what way did Princess Elizabeth's parents react to her joining the service?

What unique experience did Princess Elizabeth have on her birthday?