Tara is the daughter of Sarah FitzGerald, an artist and photographer, who is Irish and her father Michael Callaby was English. Shortly after her birth, her family moved to Freeport, in the Bahamas, where her sister Arabella was born in 1968, but the family returned to London when Tara was three.

Her mother and father separated when she was four, and along with her mother and sister, Tara moved in with her uncle Oliver Maguire (an actor) and aunt Caroline FitzGerald (a theatre director) into a basement flat off the Old Brompton Road in Kensington.

Her mother married the Irish actor Norman Rodway when Tara was six, and the birth of her half sister Bianca followed. Tara attended Clapham Comprehensive School and the North London Drama Centre. Between early acting roles she worked in Browns Boutique in Mayfair.

She has had numerous roles on British television, including Six Characters in Search of an Author, The Camomile Lawn, The Vacillations Of Poppy Carew,The Virgin Queen which also starred Anne-Marie Duff. and Joanne Whalley and beginning in 2007, Waking the Dead. Is now part of Wm. Morrison Supermarkets 2008 fresh food advertising campaign.

Her stage roles have included Blanche Dubois in an Bristol Old Vic 2000 production of A Streetcar Named Desire, and Ophelia (opposite Ralph Fiennes) in a 1995 production of Hamlet; for the latter she won a New York Drama Critics Circle Best Supporting Actress Award.

She acted in the academy award nominated Czech movie Dark Blue World and was paired with Hugh Grant in The Englishman Who Went Up a Hill But Came Down a Mountain and Sirens, the latter prompting a listing on the first FHM list of the 100 Sexiest Women in the World for her nude appearance. She also had major roles in New World Disorder and the film adaption of Dodie Smith's I Capture the Castle. Other appearances have been in Hear My Song and the 1996 film Brassed Off.