Farthing, who has been a doctor for 26 years, works at Queen Charlotte's and Chelsea Hospital in Hammersmith, west London, and St Mary's Hospital in Paddington, west London.
He became the Queen's gynaecologist, taking over care of royal mothers, in September 2008 and Kate's baby is his first high-profile royal birth.
The consultant gynaecologist, who qualified at St George's Hospital Medical School in Tooting, south London, also works privately at King Edward VII's Hospital, the Wellington Hospital in north London, St Mary's Lindo Wing and Harley Street.
He is a specialist in fertility-sparing surgery, keyhole surgery, gynaecological cancers and endometriosis.
Farthing was engaged to popular BBC presenter Dando when she was shot and killed in April 1999.
He found love again after meeting fellow doctor Janet Stowell. They married in 2008 and have a young son.
In caring for Kate, Farthing worked alongside his predecessor Marcus Setchell, who was the Queen's gynaecologist for two decades and delivered the Countess of Wessex's two children.
Setchell looked after the Duchess when she was taken to hospital with severe morning sickness in the early stages of her pregnancy.
In 2003, he helped save the lives of Sophie and her eldest child Lady Louise Windsor. The Countess was admitted to hospital after complaining of severe internal pains when she was eight months pregnant.
She was dangerously ill from blood loss and doctors performed an emergency Caesarean.
Lady Louise was born weighing just 4lb 9oz and transferred to St George's Hospital for specialist care, while the Countess remained at Frimley Park Hospital in Surrey, spending six days apart from her daughter.
Lady Louise was the first grandchild of the Queen to be born on the NHS.
In December 2001, the Countess was airlifted to hospital after suffering a potentially life-threatening ectopic pregnancy.
In 2004, Setchell was made a Commander of the Royal Victorian Order (CVO), a prestigious honour in the Queen's personal gift.
He also assisted with the Duchess of Cornwall's hysterectomy at King Edward VII's Hospital in 2007.