Marcus de Brun called for the evidence of an expert witness, Colin Bradley, who had concluded that the GP’s actions were “disgraceful and dishonourable”, to be excluded from the case against him.

An expert witness told a fitness-to-practise hearing of the Medical Council that Marcus de Brun, who operated his own medical practice in Rush, Co Dublin, had disagreed with all sorts of public health guidelines and initiatives in a large number of posts on his Twitter account.