The chapter presents the current state of research concerning the development of the BE + past participle constructions from Latin to Spanish. Starting from the description in Rosemeyer (2014) and the theoretical background collated in Kailuweit & Rosemeyer (2015), it will be shown that the functional change does not follow traditional grammaticalisation paths. Several concepts that deal with cases contradicting traditional grammaticalisation theory will be discussed. ‘Exaption’ (Lass 1990, 1997) focussing on total defunctionalisation does not account for the fact that the resultative value of the BE + past participle construction, marginal in Latin, becomes central in Mediaeval Spanish. ‘Refunctionalisation’ Smith (2008) captures this aspect in a more appropriate way. However, the development of the construction could be also conceived as the opposite of what Pountain (2000) describes as ‘capitalisation’: a process of ‘decapitalisation’ by which a feature is exploited not for wider, but for more restricted purposes.