3-Ph sub-mains on four 16mm DI singles. OK or not?

[Mark42]

I'm upgrading an existing installation in my own house, and would like a second opinion please.
An existing sub-main, in a separate building about 10m from the supply is fed via four existing 16mm DI meter tail cables in cable tray and conduit. I inherited this installation from when the very rural house was split-phase (ie L1, L2, N, E).
I now finally have a 3 Ph supply and want to exchange the remote DB for a proper 3 Ph board.
May I simply add one more 16mm DI 'meter tail' cable to the existing arrangement? (L1, L2, L3, N, E, all correctly labelled at each end).
I can't see why not. (And I do know about eddy currents and all the singles going through the same hole in any metal enclosure )
Am I missing anything?
Cheers
Mark

 

[telectrix]

see which is most cost effective, the extra single or the NYY.

 

[Mark42]

see which is most cost effective, the extra single or the NYY.

Thanks. But this is a totally separate job to my NYY question.
The latter is effectively new-build. This is a simple upgrade.

I just wondered what others' opinion of five single 'meter tails' running along cable tray then across an alleyway in conduit was. It looks ugly, but I can think of no reason why it's not OK electrically.

 

[Deleted member 26818]

Yes you can just add an extra tail.

 

[telectrix]

must be a biggish conduit.

 

[Intoelectrics]

I can't see a problem with it provided it is properly mechanically protected and supported if/where required.