The ratings success for the Channel 4 show comes on the back of a series of positive TV reviews praising the programme where millionaires give away cash to worthy causes having spent time in deprived communities.
It was the best ratings performance achieved by the programme, which is now in its third series. Including the viewing on Channel 4+1, it achieved 4m viewers and a 17.4% share.
It came despite a challenge from the first of BBC Two's new six-part celebrity reality series 'Maestro', in which eight contenders from Sue Perkins to Goldie vie to be the best orchestra conductor.
'Maestro' debuted with 1.7m viewers and a 7.9% share.
Earlier in the day BBC One's Olympics coverage brought in 2.6m and a 29.5% share between 12.45 and 5.15pm. With highlights including canoeist David Florence winning a silver medal, the British eventing team winning bronze and an individual bronze win for Tina Cook, the 7-8pm round-up programme registered 4.3m and a 22.5% share.
ITV1, which made a late change to its schedules, did disappointingly in the 9-10pm slot. Because it had decided to show football tonight, it moved 'Trinny and Susannah Undress the Nation' from tonight to last night, bumping 'Doc Martin' to the 8-9pm slot last night.
While 'Doc Martin' got 3.2m and a 14.7% share, Trinny and Susannah earned just 2.2m and a 9.5% share.
This was only half of BBC One's 4.3m viewers and 19% share for the last episode of archeological mystery drama 'Bonekickers'. The six-part series, which had a cool critical reception, had started with 6.8m viewers.
ITV1 was also beaten by Five, for which 'CSI: Miami' earned 2.3m viewers and a 10.2% share.