Raymond Baxter reports.

One baby in every 20,000 is born unable to develop mentally on a normal diet. The child is unable to digest a chemical substance present in all protein foods, and as a result the brain becomes poisoned and the child's intelligence deteriorates rapidly during the first few months of life.
Outside Broadcast cameras in the Metabolic Unit of the Little Bromwich General Hospital in Birmingham, and film cameras at the Exeter City Hospital, show some of the research going on into this disease known as Phenylketonuria.
(BBC recording)
(First shown on May 26)