The 36-year-old and Kristina, 37, attended a charity event together and allegedly left for her Brentwood apartment just an hour after arriving.
It's claimed that Ben spent the night at Kristina's before they were seen leaving separately early the next morning.
Rugby hunk Ben appeared on BBC One's Strictly Come Dancing with Kristina in 2013. A year later Ben announced his split from his wife of 11 years.
Despite this and the so called 'Strictly curse', both Kristina and Ben have always denied there's anything romantic between them.
Following Ben and Abbey's split, Kristina received regular abuse and was labelled a 'home wrecker'.
She later admitted that the allegations drove her to the brink of suicide, telling The Sun: "Nothing was ever going on between me and Ben but all this blame was piled on me.
"I was begging to quit and I had to be talked out of it. The only reason I kept going was because I didn't want to let anyone down.
"Everywhere I looked it was all wrong and all dark, and I'd had enough. I wanted to quit the show, quit everything."
At the time of his split from Abbey, a spokesperson for Ben said: "There is no third party involved, and [they] now ask that their privacy and that of their family be respected at this difficult time."