Famous Brands, the South African owner of the group, said in a recent update that this was an increase on a £3.7m loss posted the previous year.
GBK entered in to a Company Voluntary Arrangement (CVA) in November 2018 off the back of falling sales.
Though Famous Brands’ South African business remain profitable, it warned shareholders that earnings per share were set to drop by a third. This was due in part to a c.£46m write down of GBK announced in October and one-off costs of £923,000 in professional fees and redundancy costs relating to the CVA.
However, Famous Brands said in March that GBK sales had improved following the closure of 17 underperforming restaurants late last year.
It added management was “optimistic” that steps taken to save the chain were “starting to gain momentum”.
GBK was founded in Battersea, London in 2001 and was bought by Famous Brands for £120m in 2016.