There is surprising little research that directly investigates the reasons why people change their cycling behaviour. This paper presents findings from in-depth interviews that sought to understand the circumstances and factors that influenced people to start, stop or significantly change their amount of cycling. The interviews were held with residents of 12 towns and cities in England that were experiencing an unprecedented scale of investment in cycling by UK standards. The interviews collected biographical information on travel behaviour life circumstances and probed the reasons for changes in cycling. Theory and preliminary analysis were used to develop a conceptual model which posits that turning points in cycling behaviour are triggered by contextual change and mediated by intrinsic motivations, facilitating conditions and personal history. It is shown that life events were usually the trigger for a change in cycling but external changes to the bicycle environment played a facilitating role in enabling change. The types of life events that were relevant varied over the age span of participants. Practitioners can take advantage of the life events identified as opportunities to promote cycling.