Robbers forced their way into a flat and tied up the occupants before stealing valuables.

The group of seven hooded or masked men knocked on the door of a flat in Shenley Road, Borehamwood, on April 28 between midnight and 1.45am.

When a woman answered the door they forced their way in, assaulting and tying up the woman and two men inside.

All three victims sustained bruising and one man suffered a large cut to his forehead.

The thieves stole jewellery, a wallet, mobile phones and iPads.

Police have released CCTV images of men they would like to identify in relation to the investigation.

PC Mike McCoy, who is investigating, said: “I am appealing for anyone who recognises the men pictured or saw the men in the area around the time of the robbery to get in touch as you may have information that could assist the investigation.

“We are doing all we can to trace those responsible for this crime and I’d like to reassure members of the public that we believe this was an isolated incident and crimes of this type are unusual in Hertfordshire.”

Anyone with information should contact PC McCoy on the Hertfordshire Constabulary non-emergency number or contact Crimestoppers anonymously on 0800 555 111 or at www.crimestoppers-uk.org