The comedian promptly dumped his girlfriend Isabella Brewster so he could pursue his Spice Girl crush and just weeks later they're almost inseparable.
The new lovebirds have been photographed on various dates around London, including a family-style visit to Hampton Court with Geri's six-year-old daughter Bluebell Madonna.
"Things are getting very serious between them they're a proper couple now," a source told The Sun. "They had met several times in the past, but really got to know each other during the Olympics.
"People thought Russell was joking at the time, when he said he had a crush on Geri all over again, but it was true.
"They just clicked they have so much in common.
"He is spending so much more time in London just to be with her."
An eyewitness who saw the pair holding hands on their date at Hampton Court told the newspaper, "I thought it was the most random thing ever to see Russell Brand of all people in a place like that until my wife pointed out he was with a Spice Girl.
"They seemed like they were having a really great time, holding hands and chatting it was 100 percent obvious they were a couple.
"Geri was holding his hand the same way I hold my wife's. It was so cute," the witness added.