Renowned historian Michael Vickery made an eleventh-hour retreat from his decision to testify as an expert witness at the Khmer Rouge tribunal, the court announced yesterday.

Vickery, the author of Cambodia 1975-82, initially agreed to testify in June, but on July 11, he withdrew his decision, “as he thought it would be too strenuous”, according to a letter from the court.

“It is true I will not be giving testimony. That is all I want to say now,” Vickery said via email last night. The court elaborated that “he had ‘consulted with a lawyer friend experienced in these matters’ and was convinced that he should not testify”.

Vickery had previously worked for the defence teams of former Khmer Rouge leader Ieng Sary, and for Case 003 defendant Meas Muth, which prompted Muth’s defence lawyer Michael Karnavas to seek to put limitations on Vickery’s testimony, which was due to begin on August 1.

“My concerns had to do with inadvertently revealing confidential communications from having worked as an expert on the Ieng Sary and Meas Muth cases,” Karnavas said.

The announcement was met with dismay from both the prosecution and defence sides.

“We are disappointed with his decision and hope he would reconsider,” said deputy co-prosecutor William Smith.

Nuon Chea defence lawyer Victor Koppe said that it was “unfortunate”.

“He has criticised, on good grounds, many other so-called experts . . . it would have been refreshing,” he said.