Peter Hounam (left) with Mr Vanunu's adoptive parents

Peter Hounam, 60, arrived at Heathrow airport on Friday evening after spending a day in custody in Tel Aviv.

The journalist, who exposed Israel's atomic secrets in a newspaper article in 1986, was in the country to make a BBC documentary.

The source of his original story, Mordechai Vanunu, was freed from an Israeli jail on 21 April after serving an 18-year sentence for spying.

Israeli authorities eventually released Mr Hounam on Thursday and gave him a day to leave the country.

Mr Hounam, who lives in Perthshire, Scotland, said Israel should be "ashamed of itself" for arresting him and he said he was angry that he was held in solitary confinement.

Atomic secrets

He made headlines when he interviewed Vanunu and exposed Israel's atomic secrets in a newspaper article in 1986.

Under the terms of his release, Vanunu is forbidden from giving interviews about his work as a technician at Israel's nuclear reactor in Dimona.

Currently, he cannot leave Israel as the authorities say he still possesses state secrets.

But the 50-year-old says he has nothing to reveal.

Colleagues of Mr Hounam claim he was arrested by the Shin Bet security service in Tel Aviv.

At the time, he was said to be heading to a dinner meeting with Yael Lotan, an anti-nuclear activist who had lobbied for Mr Vanunu's release.

Mr Hounam's lawyer, Avigdor Feldman, said he had not violated any of the restrictions on Mr Vanunu and called the arrest a farce.