The 12th Doctor alongside his assistant Clara Oswald - played by actress Jenna Louise Coleman - brought Cardiff's Queen Street to a standstill as they filmed scenes for the sci-fi show's eagerly anticipated new series.
Pitching up outside a branch of Specsavers and employment agency Manpower, fans got to see Coleman come out of the Tardis while taking a call on her mobile phone before being followed by the Time Lord.
Coleman, dressed in a black top, tartan skirt, tights and high heels, dazzled onlookers while Capaldi looked every inch the star in the Doctor's new outfit of a dark blue Crombie coat with red lining, dark blue trousers, white shirt and black Dr Martens shoes.
Some excited fans said they braved heavy rainfall for more than two hours so they could be the envy of fellow Whovians.
Among them was engineering student James Morgan, 24.
He said: "I had no idea they were filming in Cardiff today. I was on my way to exchange a CD in town when I saw a large crowd and a film crew.
"At first I thought it might be something for Casualty as that's now filmed here.
"But I was really excited when I found out they were filming Doctor Who as I'm a big fan.
"Getting to see a glimpse of Peter Capaldi in action as the Doctor before millions of TV viewers do is amazing.
"So, I didn't mind waiting in the rain for a bit."
Grandmother and shopper Linda Powell, 66, of Cardiff, also got swept up in the moment too.
"I'm not much of a Doctor Who fan to be honest, but it was exciting to see it being filmed in Cardiff," she added.
"I don't know anything about the new Doctor really, but he certainly looked the part and I thought it was nice how he stopped and spoke to fans and signed autographs."