Police have launched an urgent appeal to locate Alexander Key, a 37-year-old chef who vanished in the Cornish village of Boscastle last Friday.
Mr Key is the long-term partner of Assisi Jackson, 33, the eldest grandchild of Rolling Stones frontman Sir Mick Jagger.
The couple shares two young daughters and resides in Cornwall.
Devon and Cornwall Police received a missing person report on Saturday evening, triggering an immediate search operation.
Mick Jagger's granddaughter's partner has gone missing
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Ms Jackson is the daughter of jewellery designer Jade Jagger, 54, and artist Piers Jackson.
Her mother is one of Sir Mick's children with his first wife, Bianca Jagger.
Mr Key is described as having a medium build with distinctive bright peroxide blonde hair.
He typically wears brightly coloured clothing and was photographed in a striking orange-patterned jacket.
According to police, he was last spotted at 2:20pm on Friday at a local pub in Boscastle.
Officers say they are growing increasingly worried about his welfare as the search continues across the area.
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Mick Jagger's family have launched an appeal
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GB News has contacted Devon and Cornwall Police for further information.
Jade Jagger used her social media platform on Monday morning to amplify the police appeal, sharing photographs of Mr Key with her followers.
Mr Key co-owns The Rocket Store, a well-regarded seafood establishment in Boscastle, alongside head chef Freddie Woodruff.
The restaurant prides itself on locally sourced produce, with fish supplied daily by Mr Key's father and meat from the family farm.
Jade Jagger (right) shared the appeal on social media
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The venue also displays artwork by Ms Jackson's father, Piers, including a star constellation painting.
Anyone with information about Mr Key's whereabouts should contact police immediately on 999, citing log number 847 of 24/1/26.