Gillian doesn’t really have to go to the premiere of her movie in London. She will only walk the red carpet and then she will go to her boyfriend’s dinner because this is much important and the movie she will find time to watch other time. Oh, and of course, she’ll change her dress in the car, leaving the premiere. This is what I heard. No joking. It was said in all seriousness. Well, I would suggest skipping the premiere altogether. Her boyfriend carries is much important, right? *kill me*

Well… the premiere is at 6pm and the dinner at 8pm. If they had to find logistic to meet each other, I would think he’d walk the red carpet with her and then skip the movie to go to his dinner. It seems like it works better this way, I wonder why no one has assume that instead of making the headcanon she will run to him as soon as she can. Her premiere might be as important as his dinner.
The thing is, actors don’t go to premiere to watch the movie or the show. They indeed have other occasions to do so and Gillian also attend the premiere in Berlin. They go because they have to, because it’s where they have to be.
This dinner is his honor, I’m sure they’ll be a table for the team of The Crown too, she might join later, who knows. There will be many celebs, people who have worked, work and will work with him there. But in any case I don’t believe she will flee from her own premiere to rush and be his date to walk the red carpet with him.