Born in 1954, Brammer was educated at the Alpha Boys School. After initially working under the name Prince Glen, he began working under the stage name Trinity, taken from the spaghetti western character. After working as a deejay on several Kingston sound systems, he made his debut recording in March 1976 with "Set Up Yourself" for producer Joseph Hoo Kim. "Words of The Prophet" followed for Yabby You, who also produced his debut album, Shanty Town Determination. Late in 1976, he joined up with Dillinger for the "Crank Face" single, and the Clash album, produced by UK-based producer Clement Bushay. 1977 saw the deejay in great demand, recording more than 20 singles for a variety of producers, including Winston Riley, Tommy Cowan, Joe Gibbs, and Yabby You, his biggest hit coming with "Three Piece Suit" for Gibbs, featuring Trinity toasting over a new version of Alton Ellis's "I'm Still In Love With You" rhythm, with a lyric that anticipated the move from 'cultural' lyrics to more material/carnal concerns of the dancehall era. This prompted an answer record from Althea & Donna using the same rhythm, in the form of the UK-chart topping "Uptown Top Ranking". Trinity recorded "Slim Thing" in response, but failed to match Althea & Donna's success. 1977 also saw the release of the Uptown Girl album, produced by Bunny Lee, and strong albums in 1978 in the form of Three Piece Chicken and Chips (with Ranking Trevor) and Showcase. In 1978, Trinity also performed at the One Love Peace Concert in Kingston. In the later 1970s, Trinity began producing both himself and other artists, starting his own Flag Man label. In 1979, he recorded the duet "Funny Feeling" with Dennis Brown, and joined up with Barrington Levy for "Lose Respect" and "I Need a Girl" in 1979 and 1980 respectively. Subsequent albums met with diminishing commercial success, and Trinity switched from deejaying to singing, releasing the albums Telephone Line and Hold Your Corner in 1987 under the name Junior Brammer.
Trinity's younger brother, Robert Brammer, also had a successful career as a deejay, recording under the name Clint Eastwood.