Natasha Walter didn’t listen when her mother, Ruth, talked of killing herself. She’d been saying it for years and though she complained of suffering from dementia there had been no formal diagnosis and her memory lapses weren’t unusual for a 75-year-old. Besides, would someone so timid and anxious have the nerve? Ruth loved her two daughters and her grandchildren, and she thought of her life as happy: why bring it to a premature end? But there had been warning signs: the pieces of jewellery she gave away; the lunch to which she invited all the family despite the lack of an occasion to celebrate; her refusal to make plans for the future. Worried, Natasha took her to lunch one day, at the end of which Ruth told her where to find the key to her locked cabinet if ever she needed it. Natasha didn’t listen to that either. Four days later Ruth took her own life, using a substance she had ordered on the internet years before. Natasha was overwhelmed with shock and grief. Unable to function at the charity for refugee women she ran, she took six weeks off work. “Crabbed” and lacking in empathy, she set about healing herself through routines of self-care: yoga, running, swimming and gardening. Soon enough, proud of her resolve and discipline, she pronounced herself cured. But she wasn’t: “I have to be honest … there is still a great, dark weakness inside me.” Along with her personal sadness she was consumed by political despair, no longer hopeful that efforts to make the world a better place can succeed. The only cure lay in listening to Ruth – in getting to know her as she really was and in understanding why her suicide note asked “Please be happy for me. It is a logical, positive decision.” Old photos were a start. More decisively, while clearing Ruth’s flat in Watford, she unearthed a document recording her arrest for civil disobedience in 1961, during a peace march in London. The arrest was the first of many. To Ruth at 19, the threat of nuclear war was terrifying and it spurred her into activism. It wasn’t enough just to march to Aldermaston or join CND. She got involved with the Committee of 100, a radical, anarchic strand of the peace movement with Bertrand Russell as its totem. Among her achievements with the Committee of 100 was the discovery of a secret government bunker near Reading – a place where elite officials could be housed in the event of nuclear war. Ruth raised the money to distribute a pamphlet about it and a media furore followed, with the “spies for peace” who broke into the bunker labelled as traitors and enemy agents. Natasha extols the Committee’s “naughty deeds” and “humorous theatricality”, which didn’t achieve the goal of unilateral nuclear disarmament but set an agenda for non-violent, Gandhi-esque political resistance which continues today. The Committee of 100 had another important outcome: it was there that Ruth met Nicolas Walter, whose lofty anti-authoritarianism was more vociferous than hers and whom she married at 20. Children soon followed, and their presence at rallies with Ruth was difficult and sometimes dangerous. Even Nicolas quietened down a little, moving the family to Harrow and becoming “an anarchist of suburbia”. The marriage ended bitterly in divorce in 1982. But, in the meantime, suburbanism didn’t defeat Ruth, who became a classic 60s boho mum, scornful of the “rituals of cleaning and fashion, grooming and consuming”, so relaxed in her jeans, sandals, anoraks and lack of makeup that she embarrassed her daughter, who briefly rebelled, once on the job ladder, by wearing Jimmy Choo shoes and designer clothes. It’s hard to believe that Walter forgot about this Ruth – tenacious, feminist, bloody-minded – a woman who managed a day centre for people with learning difficulties and who later became a social worker in a Jewish care home. But the premise of the book is a failure in understanding, and anyone who has lost a parent will recognise the shame and regret. It wasn’t just that Natasha underestimated her mother. She also underestimated her grandparents, Eva and Georg, German Jewish refugees whose experiences in 1930s Berlin had a huge impact on Ruth. On the face of it, Eva was the classic 50s housewife, vacuuming every day and cleaning the oven after each meal. Natasha remembers her sitting lipsticked and straight-backed while Ruth lolled about barefoot and braless. Ruth’s youthful political activities horrified Eva, who knew about the dangers of resistance. As a teenager in Hamburg she had dreamed of becoming a concert pianist. But nazism made that impossible. In 1939 she escaped to London. Her parents stayed behind and died in Treblinka. Georg had known Eva in Hamburg and when they met again in London they married. Eleven days after the wedding, amid paranoia about the presence of German (albeit Jewish) “aliens” in Britain, they were interned on the Isle of Man. Once released, they set up home, intent on keeping their heads down and fitting in: “Decorum had become survival.” Ruth was expected to follow their quietist example. Her teenage rebelliousness dismayed Georg no less than it did Eva. Yet as a young lawyer in Germany, he’d been angry and uncompromising too. It was only in her 50s, on a research trip to Hamburg after his death, that Ruth learned the full story of his anti-Nazi activities: of the Communist affiliations that led to his imprisonment without trial; of the 10 months he spent in solitary confinement before being found guilty of high treason and given two years in a concentration camp; of his flight through Amsterdam, Prague and Poland before reaching England. After internment, Georg changed “from hunted resistance fighter on the run to bourgeois accountant who wanted to punish his daughter for joining any kind of resistance”; the pariah became a parvenu. But Ruth inherited his spirit of civil disobedience and, Natasha, in turn, has inherited Ruth’s; she ends the memoir with her arrest during an Extinction Rebellion demonstration, “the past running through me, into the future”, her faith in “the necessity of standing up for what you believe” powerfully renewed. Heartfelt and upfront, this memoir of a mother’s suicide joins two other classics of recent decades, Tim Lott’s The Scent of Dried Roses and George Szirtes’s The Photographer at Sixteen. Among other factors behind Ruth’s death were Brexit (which destroyed her faith in Britain) and the sickness and ill-treatment Georg and Eva endured in old age (which she was desperate to avoid). It may be that this book is a stepping stone, not a conclusion, with more insights on Ruth to come: as Natasha says, “I go on walking the paths of the past, and considering them in a new light.” Before the Light Fades by Natasha Walter is published by Virago (£18.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply. In the UK and Ireland, Samaritans can be contacted on 116 123, or email jo@samaritans.org or jo@samaritans.ie. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international helplines can be found at befrienders.org.