Ben Stokes has admitted that his "head wasn't in it" during England's Test series against Pakistan, after learning that his father Ged had been diagnosed with brain cancer.

Stokes was granted indefinite compassionate leave earlier this month and missed the final two Tests of England's series against Pakistan. He arrived in New Zealand this week to be with his family, and is currently in isolation to meet coronavirus protocols.

"I didn't sleep for a week and my head wasn't really in it," Stokes told the New Zealand Herald. "Leaving [the team] was the right choice from a mental point of view."

In an interview with the same paper, Ged Stokes, 64, had told how he had been diagnosed with the illness following his return from South Africa in January, where he had been watching his son in action during England's four-Test series in the country.

Stokes senior had been admitted to hospital over Christmas, on the eve of the first Test at Centurion, after suffering a brain bleed for which he had to undergo surgery. The cancer was subsequently diagnosed after his return home to Christchurch.

"They had to assess how I travelled and from that they discovered I had a couple of tumours on my brain as well," Stokes said.

"So, basically brain cancer. How that came about nobody knows but obviously I've had a few bangs on my head through my life so that's probably contributed to it."

Speaking about his father's influence on his career, Ben Stokes acknowledged the debt he owed him for pushing him hard during his childhood, and said that his illness had redoubled his commitment to pushing himself on the field and in training.

"He was tough [on me]," Stokes said. "But as I got older I realised it was all for a reason. He knew I wanted to be a professional sportsman and he was drilling that into me as I started to make a career in cricket."

During his days as a New Zealand rugby league player, Stokes senior opted to amputate a dislocated finger in order to get back on the field quicker, and his son has a habit of celebrating his cricket milestones with a three-fingered salute in his honour.

"His reputation sort of speaks for itself," Ben said. "You speak to anyone who knows him, played with him or worked with him, they'd all say the same thing. Most people acquire a softer side with age and sometimes with dad that has been quite weird to see.

"What he's going through has brought that side out as well - we all knew he had it, he just didn't show it that often."