Though rumours are rife about a secret engagement, insiders reveal that Jemima is just good friends with Grant.
The 34-year-old and Eliot, who attended Bristol University together, were spotted at the London nightspot, Mahiki.
According to a source, the couple was 'virtually cheek to cheek'.
"Jemima was all over Ben, they looked very natural together. They were incredibly close. They were only there for about half an hour but their body language spoke volumes. It looked more intense than just a friendly chat," the Daily Mail quoted the source as saying.
"Jemima was wearing a revealing short dress with a cut-out flower shape on the front showing her cleavage. She had her hand on Ben's knee at one point and was constantly whispering in his ear. They were getting on famously."
"They were inseparable the whole time they were there and they left together. They got into a cab and drove off and they seemed keen not to be photographed too close together."
"They are both single and gorgeous, so why not? "There are definitely whispers of a romance, I've heard them, we have all heard them, but Ben is saying it's nothing serious, so it's probably just a bit of fun," another source added.
Last week, the mum of two was seen with millionaire Damian Aspinall at the Met bar on Hyde Park Corner.
However, her friends insist that their relationship is just platonic.
"Damian has been a friend of Jemima's for years and decided to be the perfect gentleman and walk her to her car," a friend said.
Grant also seems to be enjoying his newfound singlehood as he was spotted hitting a London nightspot with a bunch of twentysomethings.