Elizabeth Bee died on September 16, 1999, after becoming trapped under the school boat when it capsized in Portsmouth Harbour. Paul Dove, the teacher in charge from the pound;2,180-a-term school, failed to take a head-count and the absence was only discovered after he and the eight other pupils, including her twin sister Victoria, had been rescued.

The twins’ mother, Lesley, has said she plans to sue Boundary Oak preparatory school in Fareham, Hampshire, for her daughter’s death, after a marine accident report uncovered maintenance and spervision problems. The boat was “grossly overloaded” and in a “dangerous condition” just before capsizing, with water coming in through two small holes in the bow and because of the children’s movements onboard.

The lack of other adults to supervise the children was another contributing factor. Supervision “was at best lax and at worse non-existent”, said the report.

Head Roger Bliss said: “Many members of staff have been teaching for many years and have dedicated their lives to children. The very last thing you want to do is lose one in this way. It was a huge sadness for us all.”

The school no longer offers sailing. Mr Dove retired at 65 last summer.