The judge, Justice Jeremy Baker, sent the eight men and three women on the jury out to start their discussions at 3.15pm on Monday, seven weeks into the trial at the Old Bailey.
Old Bailey judge Mr Justice Jeremy Baker told the remaining 11 members of the jury that one of their number had fallen ill with a high temperature and will no longer be part of the trial.
The judge said: “Just to make it clear to everybody: the information we have received from the juror is she is currently running a high temperature and she has decided – quite understandably – to self-isolate so she does not risk others being infected if she does have the coronavirus. In these circumstances, it seems to me there is no real prejudice to anybody – particularly the accused – by asking you to continue as a jury of 11.”
The jury was sent home at 3.30pm and will resume deliberations on Tuesday
Duncan Penny QC, for the crown, said the brothers "stood shoulder to shoulder" in their attempts to source chemicals for the bomb.
Addressing jurors on Friday, the judge urged them to deliberate over the evidence "with dispassion and objectivity", putting aside any "sympathy for the family and friends" of the victims and survivors.