Purpose To explore the impact of interpersonal versatility on high‐value (terrorist‐related) detainee behaviour and subsequent interview information across distinct interview phases (namely the first and last interviews). Methods Police interviews with 48 terrorist detainees framework (mean number of interviews per detainee = 2.93) were coded using the ‘ORBIT’ (Observing Rapport‐Based Interpersonal Techniques; Alison et al., 2014, Psychology, Public Policy and Law, 20, 421). This produced scores for adaptive and maladaptive interpersonal behaviours of detainees and interrogators across four categories: authoritative, passive, confrontational, and cooperative. Mean scores for these variables in the first and last interviews were taken allowing us to analyse the associations between (1) interviewer behaviours and detainee educed information and (2) the indirect effect of interviewer behaviour on information educed through the impact of interviewer adaptive behaviour on detainee adaptive behaviour, separately in the first and last interviews. Results There was a positive association between detainee engagement and information in both the first and last interviews. Specific adaptive interviewer behaviours were associated with adaptive detainee behaviour in different interviews: cooperative and passive predicting improvements in the first interview and cooperative in the final interview. Maladaptive passive and authoritative interviewer behaviours were negatively associated with adaptive detainee behaviour in the first interview, as did maladaptive confrontational in the final interview. Indirect effects of interviewer behaviours on information were also demonstrated. Conclusions Interpersonal competence (avoiding maladaptive behaviour) and increasing adaptive behaviours are associated with detainee engagement and information. The differences in specific behaviours at different phases that influence information in the two interviews highlight the importance of interpersonal versatility.