Simon Cowell's talent show kicked off its eighth series with an audience share of 45% when it aired from 8pm. It gained a further 528,000 viewers (2.4%) on ITV+1 an hour later.
Earlier on ITV, 4.93m (29.7%) tuned in to see Wigan Athletic take on Arsenal in the FA Cup semi-final from 4.30pm, while new series Amazing Greys made a good start with 4.28m (20.8%) at 9.15pm.
Over on BBC One, Pointless Celebrities quizzed 4.08m (20.1%) at 7pm, while 3.79m (16.2%) watched the latest episode of Casualty.
Rob Brydon's new game show The Guess List kicked off at 9.30pm with 3.1m (15.3%).
On BBC Two, coverage from day three of Golf: The Masters pulled in 1.28m (6.8%) from 7.30pm.
Channel 4's Grand Designs attracted 620k (3%) at 7pm, followed by the penultimate episode of US drama Hostages with 570k (2.5%). Meryl Streep and Alec Baldwin's It's Complicated pulled in 900k (4.7%) from 9pm.
On Channel 5, Britain's Best Loved Double Acts entertained 670k (3%) from 7.15pm, while a repeat of Morecambe & Wise Live! 1973 entertained 579k (3.9%) at 10.10pm.
Over on the mulichannels, You've Been Framed amused 1.18m (5.8%) on ITV2.
ITV3's Rosemary and Thyme brought in 538k (2.4%) at 7.30pm, while 522k (2.2%) tuned in to Doc Martin at 8.30pm.