Q&A: Who is Constance Marten and why are UK police so concerned for her baby's welfare?

Handout file photo issued by the Metropolitan Police of a CCTV image dated January 7 of Mark Gordon and Constance Marten on Whitechapel Road in London.

Police in the UK are continuing to search for a missing baby after two people were arrested on Tuesday on suspicion of gross negligence-manslaughter.

Constance Marten and her partner Mark Gordon, who had been reported missing in January, were taken into custody after a member of the public spotted them.