In the context of UK Emergency Management, interoperability among the emergency services is essential for effective response to disasters. This study employs qualitative and quantitative observational methods, to introduce a behavioural codebook that measures physical and psychological manifestations of interoperability in cross-services operational meetings, involving the police, fire and ambulance services. Applying this coding framework, we measure the frequency of interoperability behaviour in team meetings—including markers of trust, identification, goals, communication, and flexibility (Power et al., 2024a). Through a series of multiple logistic regressions, we determine the impact that interoperability behaviour has on subsequent team interactions. Analysis of 5 high quality videos and 102 video stills showed a notable tendency for physical clustering within service units. Effective communication was the most frequently observed component of interoperability, yet it also reinforced intra-group siloed interactions. Goals were frequently discussed, and these mentions were associated with a decreased likelihood of individuals paying attention to, speaking to, and being openly receptive to members of their own service unit over others. Conversely, markers of shared identity were associated with increased cross-service physical clustering—though this did not significantly increase cross-service verbal communication or open gesturing. These results underscore the complexity of achieving genuine interoperability and the need for targeted strategies that address both operational and psychological barriers. Our study contributes to the development of practical measures for assessing and enhancing multi-agency interoperability, essential for improving emergency response coordination.