Human spaceflight is challenging and requires a large infrastructure to sustain it. For future lunar missions, the infrastructure will likely include a heavy launch system, crewed missions, the Lunar Gateway space station on its Near Rectilinear Halo Orbit (NRHO), cargo missions, and science/robotic missions. Given the mass-to-orbit required to send all this infrastructure to cislunar space, any small reduction in propellant consumption can greatly increase what can ultimately be delivered. To this end, evaluating the ΔV-optimality of the trajectories for these missions will be crucial. It will ensure the efficiency of every manoeuvre performed and every kilogram brought to orbit. Primer Vector Theory is an analytical tool which can be employed to verify the optimality of a trajectory. This approach is an indirect method which determines whether a ΔV-minimum trajectory satisfies a set of necessary conditions and can be considered optimal. Should the trajectory show non-optimal segments, additional mid-course manoeuvres can be added to reach optimality. Primer Vector Theory allows to obtain the possible locations of these manoeuvres. Once the new manoeuvres have been inserted, the difference in ΔV between the two transfer strategies can be compared. In human spaceflight, it will also be important to understand the operational implications of adding these mid-course manoeuvres should they be needed. Although the trajectory might become more ΔV optimal, when considering a flight dynamics workflow, manoeuvres need to be spaced out enough to ensure operationality. The work in this paper presents optimised trajectories to reach the Lunar Gateway from Europe’s spaceport in Kourou and then evaluates their optimality to ensure minimum transfer cost using Primer Vector Theory. The ΔV gains are weighted against the operational complexity of adding mid-course manoeuvres. In instances where the ΔV gain is deemed to outweigh the operational burden, non-optimal trajectories are re-optimised with mid-course manoeuvres. The requirements from human spaceflight constraining the choice of transfer strategy are discussed paving the way for safer trajectories.