The mother and young daughter missing from a country estate in Buckinghamshire, are believed to be the ex-lover and daughter of Viscount Adderley.
The police want to question the peer about the disappearance, but his whereabouts are unknown, and his family believe he may have left the country.
The police also confirmed that the Viscount is a main suspect in the investigation, and that they are looking closely at his movements on the run up to the pairs disappearance.