London: British pop girl group Spice Girls have confirmed their reunion as a trio to celebrate the 21st anniversary of their debut album. Members of the girl group -- Melanie Brown, Geri Horner and Emma Bunton shared photos and a video on Friday confirming the news, reports mirror.co.uk. In the clip, which they have captioned as 'GEM', Brown says: "We've been thinking. We have the best fans in the whole entire world." Horner then says: "You've stood by us for 20 years and we want to say a big thank you." They then revealed that they are holding a party and everyone is invited and hinted that they are playing London's Hyde Park for a reunion gig next July.