A mentally ill Iraqi man beat a fellow detainee to death at an immigration centre after taking the so-called zombie drug Spice, a court heard.

Zana Yusif, 32, repeatedly punched frail Bangladeshi national Tarek Chowdhury, 64, in front of his cellmate at Colnbrook Immigration Removal Centre on December 1 last year.

Mr Chowdury, who formerly worked in a fish and chip shop in the West Midlands, died in hospital following the violent attack at the centre in Harmondsworth, West Drayton, Greater London.

The defendant had previously pleaded guilty to manslaughter by diminished responsibility and appeared before Judge Richard Marks QC for sentencing.

The Old Bailey heard Yusif had a history of psychiatric problems but had stopped taking his anti-psychotic medication.

In the past he had regularly smoked Skunk cannabis and had taken the drug Spice the day before the killing.

Prosecutor Jacob Hallam QC told the court his behaviour in the wake of the attack made it impossible for him to be tested for drugs.

However, his "erratic and unpredictable" activities continued for months afterwards and could not be put down to Spice exacerbating his mental condition, he said.

The evidence Yusif had taken Spice was based on his own admission, and defence barrister David Jones said his client stood by it.

Judge Marks ordered a further medical report to be compiled and adjourned sentencing until Monday November 13.

Members of Mr Chowdhury's family had attended court for the hearing.