The Strictly Come Dancing makeup artist, 43, was seen cosying up to James Green with her beloved labrador Hurley at her side.
Now, James' estranged wife has spoken out after seeing the loved up couple on the day of her 36th birthday.
Kirsty, who was married to James for five years says she was tipped off by a pal that he and Lisa and been dating.
The mum-of-two revealed: "I saw the photos of James and Lisa yesterday - on my birthday, which wasn't the best present ever.
"I'd kind of already had an idea they were an item, someone gave me the heads up," she told the Daily Mail.
Kirsty who shares a daughter, 14, and son, 11, with James, went on to confirm that they are not yet divorced but had separated earlier this year.
She added: "We were together for a long time and I still have a good relationship with him and still speak to him. He is the father of my two children after all."
Lisa and James were snapped enjoying an afternoon stroll in a London park on Sunday, with onlookers claiming they were beaming with happiness and couldn't take their eyes off one another.
It's reported that the pair met pre-lockdown but Lisa only started seeing him when Boris Johnson announced the lockdown restrictions had eased.
Lisa and James' romance started after he had split from his wife, Kirsty.
Ant McPartlin wed Lisa in 2006 after proposing in 2005.
The pair had been together for 12 years before they announced their separation in January 2018.
Lisa is said to have received their West London home and a staggering £31 million settlement after the finalisation.
The pair continue to share custody of their labrador, Hurley.
While Ant has moved on and is in a relationship with his former personal assistant, Anne-Marie Corbett.
The pair have since purchased a gated home together and set up home.
Daily Star Online has approached a representative for Ms. Armstrong for comment.