The family of a university student who died after being restrained by police at a mental institution have said they are surprised a police investigation into his death has still not been completed one year on.

Seni Lewis 23, died after he was restrained by up to seven police officers at the Bethlem Royal Hospital in Beckenham on August 31, 2010.

The student who had recently completed a masters degree in IT and business management, had voluntarily admitted himself as a patient to the hospital, but hours later officers were called to restrain him following a disturbance.

He was taken to Croydon University Hospital after slipping into a coma from which he never recovered. He died on September 3, last year.

One year after his death, his parents and sisters Kemi and Lara, say they know nothing more about the circumstances of his death and are desperate for answers from the Independent Police Complaints Commission (IPCC).

His mother, Ajibola said: "We want to know why he was restrained by so many people. He was handcuffed, so why was excessive force used?

Seni's best friend Omari Faria, 23, added: "We don't understand why the police were called to do a job trained nurses should be doing. The police are used to restraining criminals, not patients."

The family say they have received a satisfactory report from the South London and Maudsley NHS trust (SLAM), which provides mental health services to people from Croydon, but are still awaiting reports from the IPCC and Health and Safety Executive.

They said their faith in God and the support of their pastors, church members and other family members and friends, had provided great comfort to them as they try to come to terms with Seni's tragic death.

His father Conrad, added: "We appreciate that for IPCC to do a thorough job it takes time, but we didn't think it would take this long."

Mrs Lewis added: "Nothing can bring Seni back now, but we want a conclusion and for the system to be improved so nothing like this happens again."

A spokeswoman for the IPCC said: "The IPCC concluded its investigation and passed a file to the Crown Prosecution Service on August 18 for its consideration."