Dalgliesh didn't expect that Colneth had secretly given him oral pleasure at that time.
Thinking back to when he had coerced Colneth into performing oral on him, Colneth had pretended to be extremely reluctant. Dalgliesh couldn't help but marvel at his "hidden kinkiness." This person truly had a lascivious side beneath the surface, yet he easily deceived others with his outward demeanor.
But it was precisely this contrast that aroused Dalgliesh even more. He felt his erect cock swell even more prominently, practically filling Colneth's mouth completely.
"Mmm... it's so big..." Colneth remembered the first time he had secretly licked it, just like now, he could only take in a small portion.