RBG is an exemplary documentary about an 85-year-old Grandmother, a “powerful little woman” who has become something of a feminist figurehead, liberal icon and real life superhero in America in recent years. 

RBG stands for Ruth Bader Ginsburg, a redoubtable, incredibly smart law maker still occupying her precious berth among the nine available on the US Supreme Court, where she continues to fight for equality in race and sex, against an increasing atmosphere of opposition.

Her fighting spirit and her formidable workout regime have earned her the nickname the Notorious RBG, after the rapper, who, she points out, like her, also hails from Brooklyn.

The film captures all her twinkly, inspirational candour but really concentrates on the inner steel and long dedication to her career, while showing her fruitful 50 year marriage to her out-going husband Marty and her raising of a family – I loved the moment where her now grown children recall their mother’s struggles with domestic life: “It wasn’t til I was 14 that I encountered a live vegetable,” remembers her daughter.

RBG’s early battles are soon to be the subject of a feature film starring Felicity Jones, called On the Basis of Sex, and this doc does more than whet the appetite for that, it gets to the heart of America’s conservatism and inequality while placing faith in its institutions just when they’re under fire in a new age – with a warning that power must always be held to account, with checks and human balances.