Upvote:3
Long-stay visas and residence Permits from Schengen countries (like Switzerland) exempt you from a UK Transit visa, but a short-stay visa does not
So the check-in staff were correct.
Upvote:6
Airline was right, You did need a Transit visa for the UK. See the conditions below
In the hindsight it would have been far better to have checked UK transit requirements long before going to the airport. Their website has a tool which is one of the simplest.
Was the Swiss embassy wrong?
A wrong question was put to them. They were not the relevant people to issue advice for UK visa requirements. Their answer wouldn't matter in any argument.