Episode 3 was watched by a total of 8.42 million viewers on BBC One, with a 33% share of the total TV audience. It was BBC One's second most-watched broadcast of the week and ninth across all channels.
The figure is around 2 million higher than the initial overnight rating of 6.6 million.
The consolidated figure includes viewers who recorded the episode and watched within 7 days of transmission, but not those who viewed the programme on the BBC iPlayer (900,000 within four days of transmission) or watched a repeat showing (BBC Three - 500,000).
A Town Called Mercy achieved an "excellent" Appreciation Index of 85.
On Saturday 22nd September, the episode received its Australian TV premier on ABC1 with 556,000 viewers tuning in. It was the top rating drama of the day and the ninth most-watched overall. However this is only an overnight figure, which does not take regional, rural and time-shifted viewers into account.
(Source: Doctor Who News)