Sheridan announced that she and Miles had got engaged at midday today - 1 April - by sharing a photograph on Twitter of a giant diamond ring adorning her wedding finger.
The actress told fans that the Last Shadow Puppets singer had visited her on the set of forthcoming ITV drama Cilla, which is based on the life of Cilla Black, and popped the question.
Alongside the picture, Sheridan said: "So @MilesKaneMusic just surprised me on set & proposed in front of everyone, I'm in floods & over the moon!"
Miles then replied, saying: "@Sheridansmith1 babe I'm so happy."
Sheridan also retweeted one of her followers, who said: "@Sheridansmith1 @MilesKaneMusic All the uk men are now in mourning, Sheridan Smith is off the market. All the best to you and the lucky man."
The news left fans wondering though, as no one even knew they were dating and, just four weeks ago, Miles was seen snogging Celebrity Big Brother star Casey Batchelor in London nightclub Café De Paris.
In December, Miles was also rumoured to be dating Made In Chelsea's Rosie Fortescue.
Meanwhile, earlier this month, Sheridan was romantically linked to her former Two Pints Of Larger And A Packet Of Crisps star Ralf Little...
Responding to Sheridan's announcement, one fan tweeted: "April Fool? What about Ralph Little?" Another said: "Mmmmmmm I keep looking at the date today!"
Sheridan has since tweeted: "2 years in a row baby! #aprilfools sorry, your messages were so lovely as well."
You might have fooled some, but you didn't fool us, Sheridan!
Celebrities who really have got engaged in 2014!
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