OK ... 'sleeping' policemen = undercover cops = agents provocateurs

... which would need to infiltrate Welsh institutions

... and a folk dance team would be a cultural institution fairly easily infiltrated, particularly if the cop is male 'cuz we know how difficult getting new blokes for a team is

... and folk dance teams dance at twmpathau (twmpath = mound)thus name because country dances used to take place outdoors on designated spaces (there's a proper twmpath once so used in north Cardiff/Rhiwbeina) so if

sleeping policeman = twmpath = folk dance

Yeh. See, we can prove that mathematically.

sian