Dr Williams initially developed long Covid, but for the past two years has also met the criteria for ME (myalgic encephalomyelitis), also known as chronic fatigue syndrome (CFS).

Often developing after an acute viral or bacterial infection from which people are unable to fully recover, ME has many overlapping features with long Covid.

It is estimated at least 250,000 people in the UK have ME, which affects multiple systems within the body and which can lead to symptoms like fatigue and a flu-like malaise, though the ME Association believe that figure is likely to be “significantly” higher.