When the struggle broke out on April 1, 1955, Mavrommatis joined and took part in several acts of sabotage against British military planes. He was also instrumental in the gathering of shotguns and other weapons held by private citizens. Among his companions was his cousin, Evagoras Pallikaridis, his brother and his parents.
Mavrommatis was arrested for his part in an unsuccessful attack against two British airmen in Agios Dometios. He was tried and sentenced to die.
The three men were buried in the Imprisoned Tombs in the Central Jail of Nicosia.