[3] Tannis was a member of Saint Vincent Labour Party.

[4] Tannis held many cabinet positions during Milton Cato administrations.

[4] He was also accredited as the non-resident ambassador to United States since 1981.

Tannis was Deputy Prime Minister from October 1980[5] to July 1984,[6] when Labour Party lost elections Tannis was elected to succeed retiring Milton Cato as party leader in January 1985.

[7] However, he died in a tragic plane accident on 3 August 1986 on LIAT Flight 319 when returning from Saint Lucia.