It's also important that the VFR inbound has the correct A/D in sight.
A bright, clear Summer evening; Manch, early '70s. APP hands over to TWR a non English first language DC6 off Congleton, runway in sight. Clear said DC6 to Final, RWY 24, then get on with talking to the "request start" traffic. The DC6 calls final and requests clear land. Look at the clear runway, look up the 24 glide slope; nothing. Reach for the trusty Ross 7x50s and look from threshold to Millbrook; nothing. Now feeling rather uneasy, scan entire sky from Stockport to Alderley Edge and then, just passing through the bit with Woodford in it, sight a 4 prop job climbing above the skyline off Woodford RWY 26! It caused quite a stir with the AVRO Gliding Club.