The surprise move was greeted with delight by Channel 5 staff, who see Mr Elstein as one of the most capable men in British broadcasting.
His arrival coincides with increasing financial pressures at the soon-to-be-launched fifth channel, where a high-stakes campaign to retune millions of video recorders up and down the country has got off to a slow and expensive start.
Mr Elstein said: "Channel 5 has assembled a first-class team, who are on track with the tasks facing them."
He replaces Ian Ritchie, who has agreed to stay on as chief operating officer, but who is believed by some colleagues to be likely to leave altogether.
Industry sources suggested last night that teething pains in the retuning exercise, as well as slow progress on marketing and promoting the new channel, had combined to convince the owners to replace the chief executive. The launch is scheduled for 1 January, 1997.
Mr Elstein, 51, spent the last three and a half years at BSkyB, where he was head of programmes. But his real job, in the eyes of many in the industry, was to present a more human and acceptable face at a time when Mr Murdoch's BSkyB was upsetting rivals in ITV, the BBC and the cable industry.
For the last nine months he has worked without a contract at BSkyB, and rumours that he might soon leave had been rife.
Although unexpected, the move made eminent sense to those who know him.
"David has always wanted to run a mainstream channel," one said.
Formerly director of programmes of Thames Television, he joined BSkyB in 1993. Channel 5 Broadcasting is backed by United News & Media and Pearson, owners of Thames Television.
"In a way David is returning to his roots at Thames," one Channel 5 insider said.
It is believed that BSkyB has drawn up a short list of potential candidates to replace Mr Elstein.
Speculation was growing last night, however, that the company may use his departure to engineer a general management shake- up involving further promotion of Elizabeth Murdoch, the daughter of the company's 40 per cent owner.Reuse content