The speaker is angry with someone they clearly still love. The opening lines are short and accusing: this person has wasted their youth, toys with the truth, and is "barely aloof," as if their coolness is a thin act. "Mockery of absence" is a puzzling phrase, but it suggests the other person is both gone and somehow making a joke of being gone.
Then the tone breaks. "I love you, you bloody fool" is the emotional centre, where the insult and the confession come out in one breath. The speaker admits they gave away a piece of their heart, and that it was taken. The closing image is the sharpest: that piece is now an "artefact" in the other person's "museum," something dead, labelled and displayed rather than cherished. The mood is bitter, exposed and a little sad. The clipped, stop-start lines feel like someone struggling to stay composed while hurt keeps leaking through.