In 1943, at the age of 16, Elizabeth undertook her first solo public appearance on a visit to the Grenadier Guards, of which she had been appointed colonel the previous year. As she approached her 18th birthday, parliament changed the law so that she could act as one of five Counsellors of State in the event of her father's incapacity or absence abroad, such as his visit to Italy in July 1944. In February 1945, she joined the Women's Auxiliary Territorial Service as an honorary second subaltern with the service number of 230873. She trained as a driver and mechanic and was promoted to honorary junior commander five months later.

At what age was Elizabeth when she went on her first solo public appearance?