The 27-year-old star performed some of the boy band's biggest hits during a show at the London Dungeons on Saturday night (31.10.20), but admitted he finds it "hard" to sing the tunes without his pals.
She said: "In rehearsals today I found it hard to sing the songs without the boys.
"It is a struggle, but it brings back so many memories. You’ve got to love it."
Liam - who has three-year-old son Bear with ex Cheryl - started the spooky Halloween show off in a cage, and admitted it was one of the "most weird and wonderful" performances of his career.
According to The Sun newspaper's Bizarre column, he said in a Q&A afterwards: "This is the most weird and wonderful show I have ever done.
"I don’t think I have ever started a show in a cage."
The virtual show was streamed online to fans, and it's not the first time Liam has stepped foot in the thrilling attraction.
His latest show comes 10 years after he and his fellow One Direction bandmates - Harry Styles, Louis Tomlinson, Niall Horan and, at the time, Zayn Malik, who has since departed the group - visited the London Dungeons when they were on 'The X Factor'.
One Direction were joined on the jaunt by the other 'X Factor' finalists, including Katie Waissel, Cher Lloyd, and Wagner.
The 'Best Song Ever' hitmakers embarked on a hiatus in 2016 - a year after Zayn quit the group - as Harry, Louis, Niall and Liam pursued solo careers.
Nobody is impressed by Demi "coming to the rescue".
Let's leave gatekeeping in 2020.
These are the albums we're looking forward to most this month.
David Bowie poses difficult questions about lack of racial diversity on MTV.
As Gal Gadot's Wonder Woman 1984 seems to be everywhere at the moment we thought we'd take a look back at the wonder women of music back in 1984.
Taylor Momsen radiates some seriously ethereal beauty in the video for The Pretty Reckless' latest single '25'.
The 2020 pop masterpieces that we've had on repeat.
Filmmaker Spurlock (Super Size Me) is known for his investigative wit, but there's none of...
British pop heartthrobs One Direction became a worldwide sensation when they were thrust together on...
Niall Horan, Zayn Malik, Liam Payne, Harry Styles and Louis Tomlinson may make up the...
They're the biggest boyband in the world since coming third in the seventh series of...