Unusual cable in loft

[Help!]

hi i had my loft converted professionally about 10 years ago but we still have a side loft. i was in there earlier on and noticed that the is a black flex which has colours yellow blue green none of them are connected except the yellow one which goes to a single core then runs under the floor i tested it and the is not a voltage present any one have any ideas.

any help gratefully accepted.

 

[breezer]

dont suppose you know what the other end is connected to?

if it was rewired professionaly flex should not have been used

 

[Help!]

no sorry i dont know where it goes would it be electric as the is no voltage

 

[breezer]

yes, what happens if you follow it?

 

[securespark]

Purely from the colours could this be the sort of flex used to feed central heating motorised valves etc????