Adapted from the writer Christianna Brand's series of "Nurse Matilda" children's books, this is the follow-up to the first highly successful Nanny McPhee movie. Starring Emma Thompson (who also wrote the screenplays of both films) as the eponymous nanny, this latest tale sees the Mary Poppins-esque character lend her otherworldly skills to the Green family, living in 1940s rural Britain.
And boy do they need the help. With her husband serving in the war, the hapless Isabel Green (Maggie Gyllenhaal) has to cope with handling her three boisterous children on top of keeping the family farm afloat financially. Add in her troublesome job at the local convenience store, where she has to deal with her highly eccentric boss Mrs Docherty (Maggie Smith), and the fact that her brother-in-law, Phil (Rhys Ifans), is trying to manipulate her into selling him the farm, and it's not surprising that everything is falling apart for Isabel a mere five minutes into the story.
Further problems arise when Isabel is saddled with her brother's bratty and unfriendly children Cyril (Eros Vlahos) and Celia Grey (Rosie Taylor-Ritson), when their father Lord Grey (Ralph Fiennes) sends them to live at the farm. At loggerheads with their cousins, Norman (Asa Butterfield), Megsie (Lil Woods) and Vincent (Oscar Steer) from the outset, things come to an explosive head when Cyril and Celia deliberately smash a jar of jam the children had been saving for their absent father.
It is at this point that Emma Thompson's bulbous-nosed, snaggle-toothed and warty Nanny McPhee shows up unannounced (accompanied by her magical staff and an etiquette-bereft raven) ready to impose some discipline on the household. Here the movie picks up the pace. Making herself indispensable within moments, it's not hard to see the comparisons between McPhee and that other well-known nanny figure Mary Poppins.
Both movies are overly sentimental and the plots have much in common - for example, like Poppins, McPhee also appears mysteriously when she is needed most, leaving only when her job is done. But despite the similarities, Big Bang manages to present itself as a unique and heart-warming movie. Unlike the 1964 classic, in which Poppins merely swans off into the London fog on completion of her job, McPhee goes through her own transformation as her charges grow into their responsibilities.
For every lesson (of which there are five which she repeatedly mentions) that the children adopt, one of her unappealing features disappears. When the Greens complete their last lesson, the now youthful and beautiful Nanny McPhee slips away, off to work her charms on another family in need. A unique twist on that age-old adage that true beauty comes from within, the movie is not far short of the sledgehammer school of moralising, and despite the impressive cast (which includes cameos by Ewan McGregor and Bill Bailey) and enjoyable story, older teenagers and adults are likely to steer clear as a result.
The moral is, however, presented in an unpatronising manner that makes it ideal for its target audience of tweens.