But a double-first from Cambridge hasn't prevented his double-sized cranium from developing a strange dual personality in recent months. I'm no psychiatrist or mind-reader, but the problem appears to be that one of Mr Elstein's two brains remains in the thrall of Rupert Murdoch's satellite giant BSkyB, where he was previously programming supremo.
Having worked in an earlier stage of his career at Thames Television, he should have come firmly back down to earth when he took charge of Channel 5. But, all too often, he gives the impression that his mind has been permanently altered by the period he spent on Planet BSkyB with broadcasting's version of extra-terrestrials.
The boss of Britain's fifth and final terrestrial TV channel is plainly still deeply wedded to the Murdochian dream of a multi-channel digital world - a world in which the chief task for terrestrial TV bosses would be managing decline.
Naturally, he can enthuse about Channel 5's financial prospects whenever he is called upon to do so. "It's wonderful to be launching an old-fashioned terrestrial network amid this discussion about channel cornucopia," he tells analysts and advertisers, pointing that C5 will reach three times as people on its first day of transmission (30 March, Easter Sunday) than all Sky channels. "Good old analogue telly still has a lot of life left in her."
But he becomes much more animated and persuasive when he slips back into Skyspeak and boldly prophesies the slow, steady demise of traditional TV networks and the equally inevitable rise of narrowcasting niche channels.
This struck me forcibly a few days ago when I got the chance to preview a debate on the future of television, which Granada Sky Broadcasting will screen in a few weeks time. (The programme is called South Bank Live but was pre-recorded at the London Studios last Tuesday.)
Barely had Mr Elstein pointed up the fact that three-quarters of the United Kingdom population still don't subscribe to either satellite or cable, before he was waxing enthusiastic about the inevitability of UK viewers replicating the promiscuous zapping behaviour of their US counterparts.
"If you look at countries where multi-channel choice has been available for a long time, there is every reason to believe that the consumer, given a choice, definitely wants it," he asserted.
Later, Mr Elstein - who evidently adores American TV - stated: "If you look at the United States, you will see that the four major networks have seen a consistent erosion of their audience base."
The moderator of the debate, Melvyn Bragg, missed an ideal opening to make him squirm on the end of this pointed question: if firmly established terrestrial networks cannot prevent a steady erosion of their audience (and advertising) base in the multi-channel digital universe, what long or even mid-term future can there possibly be for a fragile new network setting out with an abysmally low budget to corner just a 20th of total viewership in this country?
David Elstein is unable to answer that question convincingly because, deep at heart, he remains a Murdoch man who sees no great future for traditional terrestrial networks. BSkyB, don't forget, did not tender for the franchise to run Britain's fifth terrestrial network after Mr Elstein had spent many months drawing up a business plan.
This is not to say Channel 5 won't achieve its initial audience share target of 5 per cent, which is only half of what Channel 4 and BBC2 each achieve. Aggressive scheduling of films and football - a trick Mr Elstein learned at Sky - should ensure that its shareholders get a reasonable return in the short term.
But one can't help being deeply sceptical about the longer-term prospects of an enterprise whose chief executive has stated: "To be launching a terrestrial channel in 1997 is quite odd. But over the next 10 years, it can serve a useful purpose and became a significant asset.
"In a way we're a kind of pre-echo of what may be coming in the next year and the next decade. We're saying we're a layer of choice available free and you can have it now. Later on there will be all this other choice and it's going to cost you."
A pre-echo? If that is the most passionate and inspirational comment David Elstein can make about the first new "free to air" TV network in the United Kingdom for 15 years, it surely won't be too long before he is back in the embrace of Rupert Murdoch and his extra-terrestrial empire.
That suspicion is fuelled by the fact that Channel 5 Broadcasting and BSkyB have just joined forces to bid for the C5 text service licence. Will Sky Five Text Ltd turn out to be the harbinger of a much bigger corporate merger - headed by David "Two Brains" Elstein?n