at/in the hospital

[Anglika]

:)
I see. But the question was: should I (in BE) always use 'IN hospital' without the article while using 'the' every time I say 'AT' ('at the hospital')/
Is 'at hospital' wrong?

It will largely be governed by context.

"I haven't seen xxx for a while."
"Oh, didn't you know? He's in hospital after a heart attack."

An ongoing situation where xxxx is likely to be under medical care for more than a day.

"Where is xxxx today?"
"He's in the hospital today for an x-ray."

A temporary situation and a specific reference to the location of the event.

"Can I find Dr xxxx?"
"He is at the hospital today doing his clinic there."

It is his place of work.

I would say that "at hospital" is not a usage that you will hear.