The former beatle had smoked cannabis almost everyday since he enjoyed his first joint with Bob Dylan in the mid-1960s - but Mills McCartney was determined to create a drug-free family environment after their wedding in 2002.
She says, "Him and (his first wife) LINDA smoked it every day for the whole of their lives together. But I would not get married to him if he was taking drugs. I hate it.
"I could not have him lying to our child about not taking drugs and then going for a sneaky puff."