The leading Psychoanalyst Edna O'Shaughnessy is 90 years old today. For many this will be a cause for celebration of one of the UK's leading psychoanalysts.

For Mrs O'Shaughnessy as she is more respectfully known by her colleagues and students it will be just another day in the office as she leads the weekly clinical seminar of the Fitzjohn's Unit at the Tavistock and Portman NHS Foundation Trust.

Mrs O'Shaughnessy is a Distinguished Fellow and Training and Supervising Analyst of the British Psychoanalytical Society. She came to psychoanalysis from a background of philosophy. She moved to Britain from South Africa in the 1950s, and trained as a child psychotherapist at the Tavistock Clinic where she was supervised by Esther Bick, Betty Joseph and Hanna Segal. She then trained as a psychoanalyst at the British Society in the 1960s, with Roger Money-Kyrle as her training analyst.

One is struck not only with the clarity of her thinking but the depth of her understanding.

Mrs O'Shaughnessy has published widely. The Melanie Klein Trust says of her writings, "Reading O'Shaughnessy's papers, one is struck not only with the clarity of her thinking but the depth of her understanding and her ability to think laterally about complex issues. She conveys compassion for the anxieties and dilemmas that confront both patient and analyst, an attitude she transmits through her work as a supervisor. She also recognises the individuality of a particular patient/analyst coupling, so that the uniqueness of their encounters is acknowledged, as well as the universality of some of their struggles."

Although perhaps best known for her work with children it is through her commitment to the Fitzjohn's Unit of the Tavistock and Portman NHS Foundation Trust that I have had the good fortune to benefit from her wisdom. The Fitzjohn's unit treats adult patients who do not fit a single diagnostic group, but display and suffer from severely disorganised mental functioning. They often experience major breakdowns in relationships, work and education. Patients are likely to suffer from severe depression, anxiety, impulsive behaviours or eating disorders. Often the patients come to the unit with difficult or anxiety provoking relationships with other services and community mental health teams. Some have experienced exclusion from mental health services. For the past year I've worked as an Honorary Psychotherapist in the unit where Mrs O'Shaughnessy brings not just her immense experience but also her ineffable humanity to the work there.

She conveys compassion for the anxieties and dilemmas that confront both patient and analyst.

In a delightful discussion recently recorded between her and the psychoanalyst Ron Britton, Mrs O'Shaughnessy talks with characteristic modesty of a time when she was a young training child analyst and being 'Melanie Klein's handmaiden' at Tavistock Summer parties adding it was 'good to be in her presence'. I think all of us working in the unit experience similar benign emotions being in Mrs O'Shaughnessy's presence. I know I feel privileged to learn from her too.

Next year a book exploring the work of the Fitzjohn's unit will be published thanks to Mrs O'Shaughnessy's dogged determination. It will be a testimony to her dedication and relentless compassion in this area of work. Meanwhile, it feels like a good moment to look at her work, her achievements and her legacy and celebrate a leading light in the psychoanalytic movement.

Watch the video here, presented by The Melanie Klein Trust: The Originality of Melanie Klein: A Conversation Between Edna O'Shaughnessy and Ron Britton