Lambert has joined the TRX advisory board, joining other industry figures including Nadine Nohr and John McVay.
TRX has been set up by David and Matthew Frank who both worked with Lambert at RDF. Having created several hits for the indie, Lambert left amid a furore over a doc about the Queen.
He then set up All3Media-backed Studio Lambert, which makes factual and fact-ent hits including Gogglebox.
Lambert, who was already an investor in TRX, said: “Since I first heard about TRX from David, I’ve been a huge fan. Like all great innovations, it is simple and yet brilliant. I have become a significant investor in the business and I’m looking forward to the challenge of getting TRX established and building the company with David, Matthew and the team.
“It has huge potential to become an enterprise of real scale within a relatively short space of time – and that’s exciting.”
David Frank, executive chairman of TRX, added: “In my view [Stephen] is simply the most talented creative executive working in television today. But he combines his creative excellence with a proven and highly successful entrepreneurial instinct – getting huge satisfaction, as I do, from growing businesses.”
TRX is in testing mode with several distribution and buyer partners. The full commercial roll-out is expected in the second quarter of 2016 and, ahead of that, TRX has been staffing up.