Police say they are becoming increasingly concerned that missing student from High Wycombe, Libby Squire, “has come to some harm”.

Almost a month after the 21-year-old disappeared on her way home from a night out with friends in Hull, Humberside Police say the case “remains unexplained”.

However police say the investigation remains “very much active” and a man remains under investigation for kidnap in connection to Libby’s disappearance.

Police have now urged the public to share newly released footage of Libby – who attends Hull University – joking around with friends.

Detective Superintendent Martin Smalley, the senior investigating officer leading the investigation, said: “We have always kept an open mind as to Libby’s disappearance, hopeful we would find her and be able to return her home safely to her devoted and loving family.

“Throughout the entire investigation we have consulted with national experts from other forces and agencies as well as river and water specialists and search professionals, to ascertain where Libby may be and understand exactly what happened that night.

“Although we have followed up hundreds of leads and lines of enquiry and carried out intensive searches as part of the investigation over the last four weeks, as time passes by with no positive indication as to where Libby is or what has happened to her, Libby’s disappearance remains unexplained and we must increasingly consider she has come to harm.”

Libby’s mum, Lisa Squire, spoke of her “utter heartbreak and despair” in the weeks following her daughter’s disappearance. She described the video as “lovely” and “very Libby”.

Mrs Squire said: “It's now been four weeks without our beautiful Libby. A month of utter heartbreak and despair.

“As a family we are incomplete. We miss her more than we could ever say. We just want her back with us.

“Please if anyone has any information no matter how insignificant it may seem, contact the police.”