Since Mayadunne was the main actor during the rebellion against their father, Bhuvanekabahu VII was from the beginning suspicious of him and developed close ties with the Portuguese who had established a fort in Colombo (1517).
Mayadunne led several invasions against Kotte but Bhuvanekabahu VII was able to drive Sitawakan forces back with the help of Portuguese.
The Portuguese wanted to kill Mayadunne fearing one day he would become a greater threat to their foothold on the Island but Bhuvanekabahu VII didn't let them to conduct an all out invasion against Sitawaka.
By this time the Buddhist monks in Kotte who were responsible of the Dantha Dhathuwa, the Sacred Tooth Relic of Buddha, secretly smuggled it into Sitawaka and placed it under the protection of Mayadunne since they saw Portuguese as hostile towards Buddhism.
During the period of Kingdom of Sitawaka King Mayadunne had stopped at the Nawagamuwa Pattini Devalaya to make a vow before he went to war with the Portuguese in the Colombo Fort.
[2][3] Mayadunne and the Kingdom of Sitawaka was a part of the Sinhalese–Portuguese War, which was an effort to get rid of the occupying Portuguese forces and stop them from colonizing the island.
Due to the fact that he stood against Portuguese invaders and stopping them from conquering the whole island, Mayadunne is considered one of the greatest kings of Sri Lanka.