Roll of very sticky tape for sealing gutters, caravan roofs, etc.
I used this a few years ago to fix leaking cast iron gutters. Roll was originally 100mm wide and 8 metres long and I didn’t use very much. Tape is very sticky still so I think it’s still useable.
Waterproofing tape - BP AQUASEAL brand (Myton Park CV34)
This offer has been gifted to someone and is no longer available.