Complex sentence: The first hit (5:15am) was inflicted by a Malta-based allied aircraft (Bristol Beaufort), which immobilized the "Trento" leaving her behind while the rest of the fleet continued south in pursuit of the'Vigorous' convoy.
Split into simpler sentences: The first hit was inflicted by a Malta-based allied aircraft (Bristol Beaufort) at 5:15am. The "Trento" was immobilized and was left behind while the rest of the fleet continued south in pursuit of the'Vigorous' convoy.