The 33-year-old and former Girls Aloud star Sarah, 32, dated back in 2006 and Calum said their relationship was 'fiery, passionate and full-on'.

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He told The Sun: "My romance with her was eight months of madness. I was crazy, she was crazy and that's why we hit it off from the start.

"Goddamn, we were going out every night, we were going nuts. She was always so adventurous and it was one mad night after another. It was a whirlwind, an intense, full-on, fiery relationship. But it was good fire.

"There was always a lot of passion between us."

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Calum admitted that his relationship with singer Sarah are some of his 'favourite memories' – and told of a three-day romp with her.

He continued: "We went to this spa in the countryside and spend three whole days on our king-size bed – obviously we weren't watching TV – as well as in the jacuzzi and in the steam room.

"We didn't get dressed once, and the most either of us ever wore was a spa robe and slippers. That's one of my favourite memories."

Sarah and Calum started dating after meeting at an awards show in 2006. He said that we attracted to Girls Aloud as a whole, but it was Sarah who really caught his eye.

"We exchanged numbers and started going out. We were young, we had money and we were just enjoying life – we went for lots of dinners to Nobu and places like that," he said.

Although they were only together for eight months, Calum said that he loved being with someone as beautiful as Sarah.

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He added: "She stood out because she was so beautiful, but she'd also be the one shouting, 'Get the drinks in'.

"I was exactly the same at the time, which is why we hit it off – and also why we butted heads hard at times."

Calum said that although when they argued it could be really bad, the good times definitely outweighed the bad.

Although he wanted their relationship to work, things 'fizzled out' when Calum told Sarah – who is now in a relationship with DJ Mark Foster – he wasn't ready for anything serious.