Stefan Halper, the retired professor who allegedly worked as an FBI informant while making contact with the Trump campaign, will no longer appear at a spy forum to be held at the University of Cambridge next week.

Halper was set to attend the International Security and Intelligence conference at Cambridge in what was to be his first appearance since he was identified in the press in May 2018 as one of the FBI informants who established contact with the Trump campaign.

Several former British and American intelligence officials, including the former head of MI6, and a former deputy director of the National Security Agency, are scheduled to attend the Cambridge event.

But the Cambridge Security Initiative, which is organizing the event, now says that Halper has backed out of the event for health reasons.

“Due to ill health, Professor Halper is unable to participate in the conference,” the site says.

The Washington Times first spotted the announcement.

Halper’s role in Russiagate still remains a mystery.

As The Daily Caller News Foundation first reported on March 25, 2018, Halper had contact with Trump campaign aides Carter Page, George Papadopoulos and Sam Clovis prior to the election. It was later revealed that Halper, who worked for three Republican administrations, has been an FBI informant for more than 20 years.

President Trump coined the term “Spygate” following the revelation that the FBI relied on an informant to make contact with the campaign. Democrats have bristled at the use of the term “spy” to refer to the use of a confidential informant.

Halper first met Carter Page on July 10, 2016, at an event held at Cambridge. Former Sec. of State Madeleine Albright was the keynote speaker at the symposium. Sir Richard Dearlove, an associate of Halper’s at Cambridge and the former head of MI6, also attended.

Halper and Page met a second time on Aug. 20, 2016 at Halper’s farm in Virginia. By that point, the FBI had opened up a counterintelligence investigation into the Trump campaign. Halper and Page remained in touch through September 2017, which was the same month that the FBI stopped wiretapping Page.

One question that has yet to be answered is why Halper had contact with Page before the FBI opened its counterintelligence investigation. The bureau has maintained that the investigation began on July 31, 2016, after the Australian government provided a tip about Papadopoulos.

Halper reached out to Papadopoulos on Sept. 2, 2016 with an offer of $3,000 and a trip to London to meet in order to discuss an academic study on energy security issues in the Mediterranean.

Papadopoulos accepted the offer and met with Halper and a woman he claimed was his assistant, named Azra Turk. Papadopoulos has said that both asked him probing questions about his and the campaign’s connections to Russians.

The New York Times has reported that Turk was a government investigator, though it is unclear which agency she worked for.

A former Cambridge researcher, Svetlana Lokhova, sued Halper on May 23 for defamation. She alleges that Halper planted fake stories about her interactions with Michael Flynn during his visit to Cambridge in February 2014, when he served as director of the Defense Intelligence Agency.