Lord Janner must appear at court in person for a hearing over child sex abuse charges, Westminster Magistrates' Court has ruled.
The former Labour peer, 87, who has dementia, denies allegations of abuse in the 1960s, 1970s and 1980s.
He did not attend court on Friday as lawyers said he was "unfit" to appear.
But the chief magistrate ruled that although Lord Janner did not have to play a part in the hearing, he was legally required to attend.
Andrew Smith QC, defending, called two medical witnesses to give evidence that the former MP would suffer "catastrophic distress" if he was made to attend court.
The next hearing will be on Tuesday, which may look at other venues for the hearing on Friday next week, which Lord Janner has been compelled to attend.
The CPS said a venue for Friday could be chosen closer to Greville Janner's home.
Who is Lord Janner?
- Greville Janner was born in Cardiff in 1928
- Served in the Army and studied at Cambridge before becoming a barrister and then QC
- Labour MP for Leicester North West and then Leicester West from 1970 until retiring in 1997, when he was made a life peer
- Diagnosed with Alzheimer's disease in 2009
- Suspended from the Labour Party but will remain a member of the House of Lords until his death or until he retires
- Described by his family as a man of "great integrity" and "entirely innocent of any wrongdoing"
Chief Magistrate Howard Riddle said he understood Lord Janner "may well become intolerant of the process, irritable and may indeed leave".
He added: "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 will probably be achieved in less than a minute. Nevertheless the law requires his presence."
The case is likely to be sent to a crown court, which will decide whether Lord Janner is fit to face a trial.
Earlier this year, Director of Public Prosecutions Alison Saunders decided not to bring charges because of Lord Janner's health - but this decision was overturned after an appeal by the alleged victims.
If a crown court judge decides the former Labour MP for Leicester is fit to plead, a full trial may take place.
If not, there will be a so-called trial of the facts, where a jury will decide only if he committed the physical acts of abuse, with no finding of guilt and no conviction.
By Clive Coleman, legal correspondent
Whether Lord Janner is fit to plead - to take part in a full criminal trial - will be decided by a crown court judge. He will consider the medical evidence.
If he is not deemed fit he will face what is known as a trial of the facts. There will be no examination of the mental elements of the crime, no finding of guilt and no conviction.
It is a relatively rare procedure normally used not in cases where a defendant is said to suffer from dementia, but where they pose a danger and need to be hospitalised for the safety of themselves and others.
The court cannot impose a hospitalisation or supervision order unless a jury has found the defendant performed the physical act of the crime.
However, Lord Janner can only be sent to face the fitness to plead process and trial of the facts in the crown court, if he attends the magistrates court, or his lawyers have instructions to consent on his behalf.
If they do not, the prosecution may have to make a little used application to a High Court judge for something called a voluntary bill of indictment. This has the effect of by-passing the magistrates court and delivering the defendant direct to the crown court.