Greg Dyke was the Director-General of the BBC from 2000 to 2004. He was therefore the Director-General during the commissioning and production of series 1 of Doctor Who. However, his most inducing impact on the programme was undoubtedly the early commissioning of the BBC iPlayer — although he was not in situ for the actual launch of the service in 2007. (DOC: Interweb of Fear)
The iPlayer's impact on Doctor Who was at first slight — or perhaps just not measured well — but it went on to become a major contributor to Doctor Who's overall market reach during the Matt Smith era. Thus Dyke's willingness to take a risk on untried technology can be said to have directly helped Doctor Who's ratings — and those of many BBC shows — in the long term.