The 66-year-old singer thrilled the crowd at Hard Rock Calling when he halted a performance of his classic track 'Maggie May' to invite his "old mucker" and former Faces bandmate to play guitar on the song, which they followed with their old group's most famous track 'Stay With Me'.
Ronnie was not the only guest to join Rod on stage, with former Fleetwood Mac singer Stevie Nicks - who had played her own set earlier in the evening - making an appearance to duet on 'Young Turks' with the singer.
Despite the blazing sunshine, Rod put in an energetic performance combining greatest hits - including 'Handbags and Gladrags', 'Baby Jane' and 'Do Ya Think I'm Sexy' - and classic covers, such as 'Love Train' and 'This Old Heart of Mine', and even kicked footballs into the crowd throughout his rendition of 'Hot Legs'.
During 'You're In My Heart', the video screens flashed up images of the singer's family, including his four-month-old baby son Aiden.
Other performers in Hyde Park yesterday included Adam Ant, Train, Mike and the Mechanics and the Lighthouse Family.
Rod Stewart's Hard Rock Calling setlist:
'Tonight's the Night'
'Havin' a Party'
'This Old Heart of Mine'
'Sweet Little Rock & Roller'
'The First Cut Is the Deepest'
'Shake Your Moneymaker'
'Handbags and Gladrags'
'Someone Like You'
'Every Picture Tells a Story'
'Stay With Me'
'Twistin' the Night Away'
'You're in My Heart'
'I Don't Want to Talk About It'
'Da Ya Think I'm Sexy?'