Vast audience watched Nolan's Jonathan Bell interview

The Nolan Show Investigation programme, which included a short-notice interview with First Minister Arlene Foster filmed just prior to transmission, had an average audience of 251,000, the BBC said.

The hour-long BBC One programme, which was inserted into the schedule that morning, drew a huge number of viewers.

The BBC said that the programme attracted 56% of all those watching television at that time.

A spokeswoman for the BBC said that the network average for the same slot is for BBC One to have 18% of viewers.

She added: “These figures are based on overnights and do not include all viewers who have recorded the programme or will watch later on other platforms.”

To put the figures in context, April’s UTV election debate between the party leaders was watched by an average of 99,000 viewers, while the BBC’s pre-election debate was watched by 98,000 people.

And the programme attracted an almost identically huge audience to that for Eamonn Mallie’s interview with the late Ian Paisley, which had an average audience of 258,000 viewers, in 2014.