Any 'experts' on the Proteus?
What was the dummy ladder's purpose near Rachel Welch's seat?share
When the crew board via the top hatch it's attached to the side of the airlock for them to climb down, after which it's removed and stowed against the outer hull by her seat. If you look just after their entry you can see the empty sockets ready to hold the ladder. Presumably if the trip had gone exactly to plan they would have moved it back in order to leave the Proteus.