Diana Lamplugh: Activist whose daughter's disappearance inspired a national campaign for personal safety

Diana Lamplugh suffered any parent's worst nightmare: her beautiful, beloved and sparky daughter Suzy, a trainee estate agent, arranged to meet a client, a "Mr Kipper", at a house in Fulham, west London, on a July afternoon in 1986. She went off to the appointment and disappeared. What happened to Suzy is still not known 25 years later.

That the name of Suzy Lamplugh is so widely known is in large part due to the determination and energy her mother Diana showed. She felt an enormous desperation – "on fire" was how she described her state of mind at the time. She immediately galvanised the search, using the media and putting pressure on the police. She also sought, from early on, to find ways of preventing what happened to her daughter from happening to others.

A neighbour, Colin Morris, clergyman, broadcaster and author, was one of many who offered comfort and support. He encouraged her to channel the sudden rush of whirlwind energy for the public good. She arranged a conference in London, chaired by Libby Purves, which asked what could be done to ensure what later came to be called "personal safety". Lamplugh's energy, persuasiveness and charm drew in delegates from a variety of organisations. This led to the creation of The Suzy Lamplugh Trust.

A few months after Suzy's disappearance Paul was made redundant by the Law Society, where he had worked for nearly 20 years. This was painful, but it allowed Paul to use his administrative abilities to back up Diana's gifts of presentation and persuasion. By the end of 1986 the Trust had been formed. The Lamplughs turned their Edwardian house in East Sheen into an office, sometimes with staff or volunteers in every room. The Trust took on the task of educating trainers in personal safety; Lamplugh wrote manuals and toured the country talking about personal safety. She had a gift for finding the right people to talk to, and an ability to pick brains in an area of which she had no specialist knowledge until tragedy struck.

As a speaker she was eloquent. She assimilated information rapidly and she drove the Trust forward, co-operating with other organisations and expanding the Trust's scope without becoming territorial. There were difficult, controversial times in the late 1980s. Lamplugh's single-minded energy and lobbying gave her a high profile. In 1988 a journalist Andrew Stephen wrote a debunking book, The Suzy Lamplugh Story, which caused a great deal of pain. They had signed a contract with Faber to provide information for the book; they talked at length to Stephen but found his first draft an inaccurate portrait of both Suzy and Diana. A lengthy legal battle ensued, but the book was published. For a time the controversy disrupted the work of the Trust: at one point all four trustees resigned. However, Diana with the help of influential people, quickly found new trustees.

Lamplugh wanted, above all, to recover Suzy's body. She began to realise that the original police investigation had been flawed. This was admitted in 2002 and a review of the case was undertaken. The Metropolitan Police named a man in prison for other murders to whom circumstantial evidence pointed as the likely killer. But the evidence was not specific enough to allow a prosecution.

For 17 years Lamplugh continued the work of the Trust at an extraordinary level of intensity. She wrote many books, of which Personal Safety for Schools (1996) is probably the best known. Honours and honorary degrees flowed: she was awarded an OBE in 1992 and honorary doctorates by the universities of Sheffield Hallam, Glamorgan, Oxford Brookes and Portsmouth. These degrees gave Diana – condemned as a "failure" at school – special satisfaction.

Diana Howell was born in July 1936 in Cheltenham. Her family was of Welsh origin but had been in the town for two generations. Her father David Howell was a well-known solicitor who also loved amateur acting. He instilled into his daughter the idea of "projection". A "difficult" child, she was sent to a boarding school, Westonbirt . She was slightly dyslexic and the school failed to discover her academic potential, so she left at 16 and qualified as a secretary. After working in a school she found a more exciting job, as general factotum for the Carl Rosa Opera company. She toured Britain, often taking her Vespa scooter with her, revealing a precocious talent for organisation.

It was probably this experience which qualified her for her next job, secretary to Kenneth Adam, Cont-roller of Television at the BBC. She developed the skill of speed-reading, attacking with gusto the pile of books which arrived almost daily for her boss's attention and summarising their contents for him.

In 1958 she married a solicitor, Paul Lamplugh, whom she had met in Cheltenham. All of their offspring, Richard (born 1960), Tamsin (1961), Suzannah (1962) and Lizzie (1970), were dyslexic, and all except Suzy were sent to boarding schools with dyslexic units.

Lamplugh began to make her name as a remarkable swimming teacher. "She taught young people, the elderly, people who were terrified of water, anyone – she changed lives," says Paul. Then in the late 1960s she met an exercise guru called Pamela Nottidge who wanted to publish her popular exercises and asked Lamplugh to do the job for her by writing a book. Thus Slimnastics (1970) was born. Lamplugh began to run exercise classes. She next began to research healthy eating, then stress, and published Stress and Overstress (1974).

She set up the British Slimnastics Association which eventually trained 350 Slimnastics Leaders. By the mid-1970s she was directing huge Slimnastics rallies at the Talk of the Town in Leicester Square, at the Barbican and the Queen Elizabeth Hall.

By this time her daughters Suzy and Tamsin were late teenagers, with a frictional relationship with their parents; Diana and Paul found a delightful house in Fulham for them. Suzy had qualified as a beautician, circling the globe on the QE2. After this she took up a career as an estate agent.

On the evening of the day in 1986 when she did not come back from her appointment, Diana and Paul walked along the towpath on the banks of the Thames at Fulham, calling her name, helplessly, far into the night. But there was nothing helpless about Diana's later reaction to what had happened.

Diana had a vision of an international role for the Trust, but by 2000 she was slowing down. In 2003 she had a stroke. Then Alzheimer's was diagnosed. She moved to a care home in Twickenham. She was not able to appreciate the moment when a National Centre for Personal Safety opened in London in 2004.

Diana Howell, campaigner on personal safety: born Cheltenham 30 July 1936; married 1958 Paul Lamplugh (one son, two daughters, and one daughter presumed deceased); died 18 August 2011.