Police say they are growing increasingly concerned about four siblings who have gone missing with their father and grandmother.
The children, aged between two and 11, were last seen on 16 September leaving a property in Islington, north London.
Officers believe Tyler Jackman, Zeah Jackman, Marley Jackman and Zinayah Jackman are with Zion Jackman and Una Dolan.
The Met is appealing for help to locate the group.
The family has strong connections to the West Midlands and Essex, according to the force.
Det Insp Paul Ridley said it was "absolutely crucial that we ensure the welfare of these young children".
"If you have seen them since their disappearance or know of their current whereabouts it is imperative that you come forward and tell my investigation team."
He added that "robust action" would be taken if officers "become aware of any person intentionally assisting or facilitating their continued disappearance".
Anyone who sees the children has been asked to call 999.