A juror has been forced to leave a four-month long terrorism trial at the Old Bailey after repeatedly trying to find out if a detective who had been a witness in the case was single.

A second juror acknowledged finding the detective, DS Ryan Chambers of West Midlands police, attractive but was allowed to stay on the case after the judge, Mr Justice Globe, decided she had been forthcoming in response to questions about the incident.

Globe warned that he had considered whether he had to discharge the entire jury, abandoning a long and complex terrorism trial for the most unexpected of reasons.

A group of men from the Midlands, who called themselves the “three musketeers” in a messaging group, have spent months in the dock at the Old Bailey accused of planning a terrorist attack between May and August last year. The defence claims that the key evidence in the case, a bag containing a pipe bomb, a meat cleaver and shotgun shells, was planted in the lead defendant’s car by rogue undercover police officers.

The case, which was originally scheduled to last two months but had faced continual delays, started summing up on Monday, with the jury expected to go out for deliberations next week. One of the issues they will be asked to decide on is whether the evidence of police officers was credible.

Globe told the jury: “The information that had recently been given to me was that one amongst your number had said that DS Chambers was attractive, and another among you had then spoken to the court usher and on more than one occasion had asked the court usher to find out whether DS Chambers was single.”

The information had originated from an inquiry by the Guardian relating to an overheard conversation.

Globe continued: “The inquiries that I’ve conducted have led to one amongst your number telling me that that juror did find him attractive but had not expressed any interest in finding out whether he was single – but another juror had jokingly asked whether that was the case.

“And although the juror who found DS Chambers attractive didn’t want an inquiry to be made of the usher, nonetheless, the other juror went ahead and asked.”

No attempts had been made to seek further information about Chambers. The answers provided by the juror who was discharged were “really unsatisfactory”, Globe said. “She has not accepted that she tried to find out from the court usher on more than one occasion whether DS Chambers was single.”

He reminded the court of their responsibility to consider the questions at stake “dispassionately, impartially” and without factoring in whether they found witnesses physically attractive.

The juror who found Chambers attractive had impressed the judge with her direct answers to his inquiries, he said. Asked in a questionnaire whether she still felt she could act as a juror, she wrote: “Yes definitely!”

Globe said he believed other members of the jury may have overheard questions being asked of the usher, and he reminded them that they had a duty to report any concerning behaviour among other jurors. “To put it mildly, I am disappointed that I was not given that information,” he said. “I’ve had to ask myself whether it isn’t so important that I shouldn’t allow you as a group to continue considering this case.”

Naweed Ali, 29 and Khobaib Hussain, 25, from Birmingham, are on trial alongside Mohibur Rahman, 32, and Tahir Aziz, 38, for preparing terrorist acts between May and August 2016. They deny the charges.

The case continues.