Book excerpt: The unit-construction 650cc Triumph 'B' series twins were the top-of-the-range models in Triumph's range from their introduction in 1963 through to the introduction of the 750cc Trident in 1968. The model range outlived the Trident, grew to 750cc in 1973 and eventually went out of production in the late 1980s. This book gives a detailed technical analysis of the bikes, and charts the development of the range from its introduction through to its heyday in the late 1960s. It looks at the development of the range, and covers the various models produced including a restoration of probably the best model produced - a 1970 T120R Bonneville.