Fully independent Kingdom of Tonga
Who & why: the 1900 Treaty of Friendship with Britain is terminated by mutual agreement, and Tonga resumes full, unencumbered independence on 4 June 1970, joining the Commonwealth shortly after. Because Tonga's monarchy had governed continuously and never ceded sovereignty even during the protected-state period, 1970 marks a return to full external freedom rather than a first grant of self-rule.
What it represents: the same red field and white canton with a red couped cross that King George Tupou I fixed by law in the 1875 constitution — a design that has now flown, unaltered, through protected-state status and full independence alike.
Both sources date the current flag to 1875, before this era begins in 1970, so the flag was already in use at the start. Wikipedia's infobox gives the adoption as 4 November 1875; Flags of the World dates it November 1875.
- Flag of Tonga — Wikipedia compiled
- Tonga — Flags of the World (CRW Flags) compiled
Not established: Only the year the current flag was adopted was compared; the design and the swatch colours were not checked against a specification.