after hearing a scratching sound from behind the air vent set in the wall, I got out the steps and had a look and could just make out a shape of a bird against the outer grill,
I had to lever the air vent from the wall, and try and grab the bird, but it fluttered down the cavity and out of reach, I thought that's it I will not be able to get it out now, but decided to wait and see if it could get back to the vent,
on hearing a faint scratching , I got back up the steps to see it crawling up the cavity , looking more like a bat than a swift!
a quick grab, but missed it again,
as I did not want it to get out into the room and possibly injure itself in a panic to escape I taped a sheet of paper loosely over the hole and sat back to see if it would reappear,
after half an hour I could hear some more scratching sounds from behind the paper, a quick peep showed the bird clinging to the outer vent, so a quick grab and success, one swift in the hand
out into the garden, and after a quick inspection, it seemed uninjured, so a toss into the air and away he went to be joined by several more swifts screeching away

hopefully, cavity wall insulation (to be carried out in winter to avoid disturbance to nesting swifts and sparrows) will prevent a recurrence of this possibly lethal situation for the swifts, as this is the second one we have rescued from the vent ,
now its a trip to b&q for a plastic air vent (to replace the plaster type one which I damaged beyond repair) which can be removed if needed, until the cavity insulation is done.
what a pleasure to be able to save one of these remarkable birds, and even more so to actually have one in the hand
