Withdrawn from Chester in 1973, 55997/9 in October and 55998 in December (due to fire damage?), mainly because they were non-standard.
55997 went into departmental use, and was cut up at Vic Berry's in 1986.
55998 apparently became an internal user vehicle in July '73 but was sold and moved to Cohens of Kettering by 11/75.
55999 had been broken up 9 months earlier in Feb '75 at Derby Litchurch Lane Works (although I've seen a photo of the stripped out vehicle there dated August '76).