I arrived at LHR in March 99.
I got involved, along with a colleague who was a matter of a 6 months more experienced than I was. We put our hands up when volunteers were sought. There was also a selection process to go through. I believe there was a push to ensure that some of the interviewers had recent experience of the training system. As an interviewer, I had a total of five days training over two different courses before being let loose on the candidates.
I remember on one of those training courses I got to meet the ATCO who had interviewed me, whom I hadn't met since that day, so that was actually very rewarding.