Oh I think I understand now ! So the 3HRS 45MIN delay for the CFU to BHX flight reported by the op was actually caused by a delay in the initial BHX to CFU leg.
Now that raises another question - I’d think that the crew was meant to fly both legs. That’s 2x 3:15 (approx), plus turnover, preparation etc we are getting close to 8h. Are we to understand that they were operating another rotation before (presumably a short one) ? Those are pretty heavy work days :/