The late, great comedy partners Peter Cook and Dudley Moore once performed a sketch on BBC TV in which the letter R had fallen off a sign, causing Cook in his "Pete" persona to remark on how very unfortunate it is if you "let your Rs fall off".

This harmless-enough rude joke came to mind recently when I heard another Pete on the BBC - Rabbi Pete Tobias of the Elstree Liberal Synagogue - this time on the radio. I have never met Rabbi Tobias, and the little I have heard about his rabbinical qualities has been entirely positive, but I have always been uneasy about his calling himself "Pete". Somewhere, sometime, his "r" has fallen off.

From his photograph, Rabbi Pete looks extremely cheerful. But there are many times in a rabbi's life when he (or she) needs to be taken very seriously and I confess I would find it hard to do so when the rabbi is called Pete. "Pete" is a cowboy, a rock singer, a tennis player; not a rabbi.

I realise that, in a world where an American President called Bill and a British Prime Minister known as Tony have already cemented their names in history, I am out of step with the times. (The difference in the Milibands' first-names is one of several reasons why I am disappointed that Ed beat David. ) Only last month, the authorities at a primary school in Kent decided that its pupils should address their teachers by their first names, in order to "improve relationships between students and staff".

I wonder. Informal relationships are undeniably the most agreeable kind, but not all relationships work on an informal basis. Maybe it is as a result of my own schooling that it seems to me that the teacher-pupil relationship is one such, especially at the primary level. I certainly hope that those Kent kids don't go beyond their teachers' birth-certificate names and refer to them as, say, "Jimmy" or "Jackie", as if they were playground chums rather than their educators.

The rabbinate, too, is surely an essentially formal profession. Its Orthodox practitioners, perhaps unsurprisingly, do seem to reflect this. Rabbi Geoffrey Hyman of Ilford isn't Geoff. Michael Harris of Hampstead isn't Mick. Edgware's David Lister isn't Dave. And can you imagine "Chief Rabbi Jonny Sacks"?

Reform, by contrast, have the likes of Larry Becker in Wanstead, Danny Burkeman at West London, Bromley's Tony Hammond, and the Tabicks - Larry in Hampstead and Jackie in Weybridge. Rabbi Tobias's Liberal colleagues include Ron Perry at Bristol and Kingston's lady rabbi, Charley Baginsky. That leading Liberal figure, the late Rabbi Sidney Brichto, would quite possibly have approved of all this informality, but would anybody have countenanced calling him "Rabbi Sid"?

Strangely enough, "Jonny" would rather suit Masorti's Rabbi Jonathan Wittenberg, blessed as he is with a naturally informal charm (and, like Rabbi Pete, a children's book author). And of course I do appreciate that any rabbi's effectiveness in the role is much more important that what he or she is called. The brilliant Kol Nidrei sermon - a perfect mix of the personal and the public, of profundity and entertainment - delivered this year by the Reform movement's prime preacher Tony Bayfield, could not have been bettered by an "Anthony".

I have never witnessed Rabbi Pete Tobias at work, and I caught only a snatch of that recent radio broadcast. For all I know, he may be capable of rising to Bayfieldian or Sacksesque heights. But this is much harder to accomplish if you let your Rs fall off.