I had lightbulb in my bathroom that lasted for many years but finally blew. I took the blown lightbulb to the lighting store, and they gave me a replacement that they said would work.
However, I then found that the new bulb wouldn't fit into the light fitting. In short, the red line depicted below is shorter than the yellow line.
I'm confused about whether I should press hard on the copper-colored metal to push it apart (I think that's doable, though I'd have to push really quite hard) or whether maybe the lighting store were wrong and I have the wrong type of bulb.
As per the request in the comments I have taken a photo of the whole fitting, and have looked at the numbers underneath.
PAT APPL 42845764
CAT No 60720 240V 60 W AC
SEC APPROVAL No CS 0799