Conversation so far:
How were the Sinhalese kingdoms formed?
Sinhalese kingoms were formed by Prince Vijaya and his 700 followers. They left Suppāraka, landed on the island and founded the Kingdom of Tambapanni.
Who or what are the Tambapanni in relation to the Sinhalese people and their kingdom?
Vijaya claimed Tambapanni his capital and soon the whole island come under this name. Tambapanni was originally inhabited and governed by Yakkhas, having their capital at Sirīsavatthu
Is Tambapanni where the Sinhalese live today?
Who is Vijaya in relation to the Sinhalese people?
Prince Vijaya was the traditional first Sinhalese king of Sri Lanka
Did Prince Vijaya take over the Sinhalese people?
Prince Vijaya was the first king of the Sinhalese people during the Pre Anuradhapura period
Were the Sinhalese people always at Tambapanni?
Before the Sinhalese, Tambapanni was originally inhabited and governed by Yakkhas, having their capital at Sirīsavatthu and their queen Kuveni.
How well are the Sinhalese people doing now?
The Sinhalese have a stable birth rate and a population that has been growing at a slow pace relative to India and other Asian countries.
Are the Sinhalese people people thriving presently?
Sinhalese people have emigrated out to many countries for a variety of reasons. They are often employed as guest workers in the Middle East and professionals in the other regions.
Are there any other interesting aspects about this Sinhalese people histoy article besides that the Sinhalese people have emigrated out to many countries for a variety of reasons. They are often employed as guest workers in the Middle East and professionals in the other regions?
At the end of his reign, Vijaya, having trouble choosing a successor, sent a letter to the city of his ancestors, Sinhapura
Did Vijaya choose anyone as successor over the Sinhalese people?
Vijaya wrote to invite his brother Sumitta to take over the throne as successor over the Sinhalese people
Did Sumitta take over Vijaya's throne anyway?
Vijaya had died before the letter had reached its destination, so the elected minister of the people Upatissa acted as regent for a year.

Question: Who was the elected minister?
Self-contained rewrite: Who was the elected minister who acted as regent for a year for the Sinhalese people?