LILY ALLEN has finally come clean about her fling with Liam Gallagher – when he was still married to Nicole Appleton.

In her explosive autobiography, Lily admits she did romp with the Oasis star on a flight to Japan in July 2009.

She also teases that it happened again after they arrived, and claims Liam later got her to lie to the All Saints singer telling her it had never happened at all.

In her book My Thoughts Exactly, Lily recalls that eventful journey to the Fuji Rock Festival.

She writes: “We got hammered on the plane. At some point Liam and I found ourselves together in the toilet doing something that he shouldn’t have been doing, and it wasn’t drugs. Then we were in a lie-down bed together.

“When we landed in Tokyo, Liam said, in his distinctive nasal twang, ‘What you doing now? Why don’t you come back to our hotel . . .  I was like, ‘Yeah, OK.’

“It wasn’t until the next day when he said something like, ‘No one can hear about this because of Nic,’ that I clocked he was married. I knew Noel was married and I knew Liam had been married to Patsy Kensit. That was partly why I fancied him. I’d grown up an Oasis fan. I was 12 when he and
Patsy Kensit were on the cover of Vanity Fair as the coolest couple.”

But Nicole got wind of what had gone on. Lily adds: “Six months later I was in my car with my driver when the phone rang. . .  It was Liam.
He sounded awful, like he’d been up all night. ‘Lil,’ he said. ‘I just need you to get on the phone. I’ve got Nic here,. One of your mates is, like, trying to do a wind-up or something and saying that you and me had it off or whatever, and I need you to speak to Nic and say that it’s all b*****ks.’

“Oh, Liam, yes sure, it’s all b*****ks. Let’s say it’s all b*****ks — of course I’ll tell Nicole that it’s all b*****ks if that’s what you want — and not think about it too much or even at all, and then maybe it will go away and not disrupt what really matters: The people we love and rely on.”

The Sun on Sunday told how Lily was poised to reveal their affair in April when she touted her book to publishers.

Nicole, who divorced Liam, left, in 2014, warned: “One day our paths will cross @lilyallen!”

Lily writes: “Surely part of the point of shagging Liam Gallagher is being able to tell your friends about it . . .  It’s so depressing, isn’t it?

Why do we validate ourselves with our sexual conquests? But actually we are just as bad.”

At least Lily can bring out her poison pen for a quick quid.