Stella McCartneyStella McCartney has become a mum again for the third time after giving birth to a baby boy in London this week.

The fashion designer and husband Alasdhair Willis welcomed son Beckett Robert Lee into the world on Tuesday, a younger brother for almost three year old son Miller and one year old daughter Bailey.

Beckett is a fifth grandchild for Stella’s dad, Paul McCartney.

A source close to the family revealed: “Mum and baby are doing just great and everyone’s thrilled about the new arrival.”