Lord Janner has been ordered to appear in court in person for a hearing over child sex charges despite suffering from severe dementia.

The former Labour peer and MP did not attend Westminster Magistrates’ Court for an initial hearing today, with his lawyers saying he was too ill to come and may suffer a “catastrophic reaction” if produced.

But chief magistrate Howard Riddle ruled that Janner, who faces 22 charges spanning a period from the 1960s to the 1980s, did not have to understand or play a part in the initial hearing but was required by law to attend.

The court has adjourned to allow lawyers to determine when he might appear.

Mr Riddle heard evidence from two defence medical experts who said Janner was too ill to appear.

But he said that while there was “absolutely no doubt” Janner suffered from severe dementia the section 51 hearing “does require the defendant’s presence”.

He agreed with the prosecution’s argument that many defendants find court appearances distressing and that after their initial short appearance at magistrates courts means were found to accommodate them.

Mr Riddle said: “I have heard evidence from the two experts that in the context of today’s hearing there is likely to be distress and that is what has been described as ‘catastrophic distress’.

“But what it means as I understand it is that the defendant may well become intolerant of the process, irritable and may indeed leave.

“I further understand, and this is very significant, it is likely to have no long term effect on him.

“He must appear for a comparatively short period of time. He is free to go if he becomes distressed. This (hearing) will probably be achieved in less than a minute. Nevertheless the law requires his presence.”

In April, director of public prosecutions (DPP) Alison Saunders announced that Janner, 86, would not face trial over allegations he abused children in Leicestershire children’s homes in the 1970s and ‘80s because he is suffering from Alzheimer’s disease.

But in June, the CPS announced that criminal proceedings would be brought against the former Leicestershire MP, whose home in West Heath Road, Hampstead, was raided by police investigating the allegations in 2013.

It followed an independent review of the DPP’s original decision which was called for by alleged victims.