Prime minister David Cameron and his wife Samantha hosted the event, also attended by supporters and beneficiaries of the charity, which raised £46m in its most recent appeal.
Barlow, who organised The Collective's charity cover version of 'Teardrop' along with the Children in Need Rocks Manchester gig, was greeted by the couple.
"I am delighted to see you all here and to be supporting this truly fantastic charity," Samantha Cameron told the guests. "BBC Children in Need's vision is that every single child in the UK has a safe, happy and secure childhood and the chance to reach their potential.
"Since 1980 BBC Children in Need has raised over £600 million that has helped transform the lives of tens of thousands of children and young people."
She continued: "BBC Children in Need's record-breaking appeal in 2011 means they'll be awarding a staggering £46 million this year to large and small groups all over the country.
"The charity relies completely on the energy and generosity of their supporters, the incredible people who work in the 2,500 projects they are currently funding."
Andre, who performed in West End musical Ghost to raise money, commented: "People talk about Britain being broken and all these things but get them to dig deep for Children in Need and look what they do."
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