Kate sick, not there for Prince George's first day of school

Britain's Prince William accompanies Prince George as he is met by Helen Haslem - the head of the lower school as he arrives for his first day of school at Thomas's school in Battersea. Photo / AP

Prince George has walked nervously into school on his first day with his father by his side but without his mother, the Duchess of Cambridge.

Kate had hoped to join the Duke of Cambridge on the school run but is suffering from severe morning sickness and was too ill to attend, Kensington Palace said.

The four-year-old prince was helped out of the car by William after being driven through the gates of Thomas's Battersea, a fee-paying independent school in south London.

The prince would be known as George Cambridge to his classmates, the palace said.

Photo / AP

George looked tentative, clutching his father's hand, as he was led towards the school entrance.

The young prince shook hands with Helen Haslem, head of the lower school, as the Duke held his school bag ready for his first day.

Kate had hoped to join the Duke of Cambridge, but she remains unwell after the announcement she is pregnant with her and William's third child. Photo / AP

- AAP