The Citigate Dewe Rogerson consultant is viewed by some as having played an instrumental role in building the mobile network from tiny start-up to the largest operator in the UK, through two separate flotations and three changes of ownership.
Certainly, his resignation of a long-term, half-a-million-a-year client will have raised eyebrows in the Square Mile, although sources close to Carlisle insist the money was never an issue, and hint there may be other mobile firms waiting in the wings to fill the gap in the revenue line.
The reasons Carlisle's friends give for him wishing to extract himself from Orange will give cheer to purists in the industry, and strike fear into the hearts of less scrupulous PROs who fear that Carlisle's reasoning, sincere or not, may become the norm.
In short, he is believed to have felt that having sold telecoms journalists a particular line over the years, he couldn't credibly change his patter to reflect Orange's looming change of strategic direction.
The precise details of Orange's imminent conversion are not at issue, but the question of how easy it is for a PRO to lose credibility is essential.
Although the circumstances of Carlisle's split from Orange are rare, bordering on unprecedented, at its core is a deeply familiar issue: whether the PR consultant is brought in by management to polish and flog existing messages, or to help formulate the strategy which those messages describe. Carlisle rightly considers himself in the latter of the two camps.