Born: 16th March 1943 (as John Francis Christopher Ducker)
Episodes Broadcast: 1977-1979, 1980-1981, 1983, 1993, 2006-2010

Born in Leicester, Leicestershire, the young John Ducker worked in a bookshop and as a hospital porter while performing with the Leicester Dramatic Society. Eager to make a career as an actor, Ducker was accepted to the Royal Academy of Dramatic Art. It was there that he adopted the stage name “John Leeson”, derived from the surname of a wealthy godmother whom he believed was funding his tuition. Graduating in 1964, he worked several seasons in repertory theatre, while his first television role was in the 1965 musical Meeting Point. Other Sixties appearances included episodes of The Spanish Farm, Dad's Army and a brief run on the soap opera Crossroads; Leeson also worked as a BBC continuity announcer.

As the decade came to a close, Leeson was enjoying more prominent theatre roles, including Neil Simon's Plaza Suite in 1969. The same year, he married Judy Griffiths, a BBC assistant who later worked as a props buyer for movies and television. They would have a son, Guy. In 1972, Leeson's vocal work was on full display when he occupied the Bungle the bear costume for the first season of the children's programme Rainbow. Other credits during the first half of the Seventies included The Doctors, Take Three Girls and two installments of Comedy Playhouse. Leeson also provided more than twenty thousand questions for the quiz show Mastermind and moonlighted as a photographer, snapping actor's portraits for the Spotlight directory.

Leeson would get down on his hands and knees to fill in for the K·9 prop during rehearsals

1977 proved to be a watershed year for Leeson's career. Not only was he busy on-screen in episodes of Headmaster, The Foundation and Crown Court, but he also persuaded a friend from his repertory theatre days, director Derrick Goodwin, to find him work. Goodwin offered Leeson not one but two voice roles for the Doctor Who serial The Invisible Enemy: the villainous Nucleus of the Swarm and the robot dog K·9. The latter was so popular with producer Graham Williams and script editor Robert Holmes that he was made a permanent addition to the TARDIS crew. Leeson provided his voice for three further serials during Doctor Who's fifteenth season. In the process, he endeared himself to cast and crew by getting down on his hands and knees to fill in for the K·9 prop during rehearsals. Leeson then returned for the entirety of Season Sixteen. However, because K·9 could not plausibly appear in the swamp-set The Power Of Kroll, it was decided that Leeson would instead have an on-screen role as the ill-fated Dugeen.

By this time, Leeson was becoming concerned that a lack of visible roles might hinder his future employment. As such, he left Doctor Who, with David Brierley voicing K·9 during Season Seventeen. Leeson could be seen in programmes such as Blake's 7 and Rings On Their Fingers, while vocal roles included Jigsaw and the movie Tarka The Otter. Leeson then agreed to reprise his role as K·9 for a valedictory run in Season Eighteen, culminating in the robot dog's departure in 1981's Warriors' Gate. That Christmas, the BBC broadcast A Girl's Best Friend, the pilot for a proposed spin-off called K·9 And Company which also featured Elisabeth Sladen as former companion Sarah Jane Smith. However, it was not taken up as a series.

Work during the rest of the Eighties included The Barretts Of Wimpole Street, Whoops Apocalypse and 'Allo! 'Allo!. Leeson also returned to Doctor Who twice, as K·9 in the twentieth-anniversary special The Five Doctors and then voicing the Dalek battle computer in 1988's Remembrance Of The Daleks. Amongst Leeson's Nineties credits were episodes of The Bill, Minder and Bugs. He played K·9 two more times, first for an installment of the children's programme Search Out Science in 1990 and then for the 1993 charity special Dimensions In Time. Leeson also joined other Doctor Who alumni in the 1995 Reeltime Pictures video drama Downtime. Although his on-screen career was beginning to wind down, Leeson kept busy with work as a food writer, a wine lecturer and a justice of the peace. He also twice ran for Ealing Council in the Perivale district, unsuccessfully representing the Liberal Democrats. Nonetheless, the new millennium brought credits on Longitude, Doctors and ChuckleVision.

The return of K·9 in School Reunion won Leeson a new generation of fans

Perhaps inevitably, it was K·9 who loomed largest in Leeson's twenty-first-century portfolio. He had already begun reprising the role in Doctor Who audio dramas, beginning in 1999 with the short-lived Adventures In A Pocket Universe range, an unofficial spin-off from BBV. In 2003, Big Finish Productions recruited Leeson for an audio adaptation of the unfinished Season Seventeen serial Shada; he worked frequently with them thereafter. But it was the surprise return of K·9 in 2006's School Reunion which won the robot dog -- and Leeson -- a new generation of fans. Leeson was soon voicing K·9's occasional appearances in the spin-off show The Sarah Jane Adventures, alongside a final Doctor Who cameo in 2008's The Stolen Earth / Journey's End. Leeson was also the voice of an updated version of the metal mutt for K·9, which was produced in Australia and aired for a single season starting in 2009. Most recently, Leeson could be heard as K·9 in 2013's The Five(ish) Doctors Reboot, a spoof which aired as part of the show's golden anniversary celebrations.

In 2011, Hirst Publishing released Leeson's autobiography under the title The Flight Of The Budgerigar. An updated and extended version, now called Tweaking The Tail, was issued two years later by Fantom Publishing. In 2014, Fantom released a collection of Leeson's favourite recipes as Dog's Dinners.