GreyLord
Legend
Well, that seems accurate.Get out. The show was at it's height during the Tom Baker era.
The all time highest viewed episode seems to be with the 4th doctor City of Death 4th episode with 16.1 viewers.
Right behind was part 3 with 15.4 million viewers
Destiny of the Daleks had 14.4 million viewers
In fact, the 4th doctor seems to have consistently brought in over 10 million viewers and often between 12 to 13 million viewers though occasionally it fell to 8 million and his last season seems to have an average of 5-6 million viewers (and that explains the real reason why they shifted to getting a new doctor probably, though it was a temporary fix where he had around 9 million viewers on average his first season and around 7-8 million on average the following seasons).
The highest viewed of the New Who is under Tennant with a Christmas Special with 13.3 million viewers. Most of those in the top 25 which have over 10 million also have Tennant in them, though there is one of those with Matt Smith in it as well (take a guess which one).
Tennant seems to be the high water mark for the New Who averaging between 7.5 - 8 million veiwers on average during his seasons. Matt Smith is close, but averages around 7.5 to 7.75 million viewers on average.
One major surprise....the first season of the 13th doctor (the 11th series) actually has the MOST average viewers since Tennant's high water mark, at 7.96 million viewers on average. It has fallen since then but was interesting to see.
It also appears that when a new doctor comes around, the viewership jumps up (at least for a season) on average (with the exception of the 6th doctor), so in the next series (series 14) if the stories are true and the 13th doctor is leaving the show and a new one comes on, I expect the numbers to jump up again at least a little bit for the 14th doctor.
For the average numbers I took them from this source...
Wikipedia Doctor Who episodes