Andy Burns wrote:
Phil L wrote:

Unscrewing the screws won't get you anywhere as it's an inset lid

Maybe you're then supposed to screw some handles or hooks or something
into the threaded holes?

Maybe, but in 25 years of installing these things I've never seen one like
that.

Normally, there's a black plastic strip, which is prised off with a flat
driver and underneath is a lift handle that pulls up, there's one on each
side.

Other than that, they sometimes have a welded steel plate covering about
40mm of opposite corners and this plate has a hole in it in which a suitable
shaped lump of metal is inserted and lifted.

this thing looks like the lifting mechanism is along each side inbetween
these screws - the pointing is particularly wide here....although like i
said, I've never seen one like that.

It is of course a possibility that the screws themselves are the lifting
mechanism and are not meant to be moved, I'd scrape around and under each
one and insert a suitable rope / cable / whatever and lift it out that way.