In 1965, she followed Wolff to Great Ormond Street Hospital in London, and the associated Institute of Child Health at Imperial College London where she became a senior lecturer, later a reader and finally professor.
Lloyd was appointed professor of child health and head of a new department of paediatrics at St George's Hospital Medical School in London in 1975, and returned to Great Ormond Street in 1985 as Nuffield Professor of Child Health. She served with distinction on many committees. She was the first female president of the British Paediatric Association from 1988 to 1991, and was a vice-president of the Royal College of Physicians from 1992 to 1995.
She retired from practising medicine in 1992, but played a role in transforming the British Paediatric Association into the Royal College of Paediatrics and Child Health, to take over responsibility for training and standards for paediatricians that had previously been under the control of the Royal College of Physicians. She is commemorated in the coat of arms of the new College, in which she is a supporter holding a staff of Aesculapius entwined with a double helix rather than the traditional snake. The other supporter is Thomas Phaire, whose Boke of Chyldren from 1545 was the first book on paediatrics in English; the crest is a baby, taken from the arms of the Foundling Hospital in Coram's Fields.
Lloyd was appointed a DBE in 1990, and received an honorary DSc from Bristol University in 1991 and a second honorary DSc from Birmingham University in 1993. She was made a Life peer as Baroness Lloyd of Highbury, of Highbury in the London Borough of Islington in 1996.
However, a severe stroke before her introduction to the House of Lords prevented her taking her seat until 1998. Her resulting disability left her unable to become an active member of the House. She died on 28 June 2006, aged 78.