A tripartite agreement was signed by Belgium, France and the UK on 15 May 1993, which permitted British officials to carry out pre-embarkation immigration controls for passengers travelling on direct Eurostar train services from Brussels to London and Belgian officials to carry out pre-embarkation immigration controls at London Waterloo International (and subsequently St Pancras International) station for passengers travelling in the other direction.
On May 15, 1993, a tripartite agreement was signed by Belgium, France, and the UK, granting British officials the authority to conduct pre-embarkation immigration checks on passengers traveling on direct Eurostar trains from Brussels to London, while Belgian officials were granted similar rights at London Waterloo International (and later St Pancras International) station for passengers traveling in the opposite direction.