To the OP, if born in 1980 then you are getting close to 30 !
28-30 seems the most popular age for career men to get married in the UK. Weddings cost about £20,000 on average and the bride's family often dont or cannot pay.
Back to your boiler, if its gas sealed on the inside with plaster then its not unsafe in any way. Wrong, but....
However, it should be cemented on the outside to prevent water ingress into the wall.
The rubber gasket is not required in your case so you can take it off and chuck it away when you cement the gap.
In spite of what has been said above the silver part at the end gets to about 120°C so it can burn you apart from gassing you!
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