The launch show ratings were down from last year's 5.4m audience, and well short of the 6.2m that BB8 kicked off with in 2007.
Last night's introduction of 16 hopefuls was watched by 22.1% of the total audience and around 40% of the 15- to 34-year-old viewers watching television at the time.
Its repeat on Channel 4+1 also picked up 288,000 viewers.
ITV1 was Channel 4's closest challenger with 3.3m viewers and a 14.7% share for 'Taggart' at 9pm-10pm.
In the same slot on BBC One 'Calendar Girls: 10 Years On', which looked at the Women's Institute members preparing to strip again for another charity calendar, managed 3m viewers and a 13.5% share.
'The Mentalist' continued its decent performance for Five at 9pm-10pm with 2.4m viewers and a 10.6% share.
BBC Two trailed with 1m viewers for a harrowing documentary about women who self-harm. 'A World of Pain', fronted by Meera Syal, was watched by 4.5% of the audience.
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