Hope this one is the one you're looking for?
Wharf:Clelands S.B. Co.Ltd.-Wallsend
LOA x B x D:91.24 x 13.47 x 5.146
Owner:London & Rochester Trading Co.Ltd.
Eng:Vee Oil 4SA 16Cy.250x300 reverse reduction geared to sc.
2,089kW[2 800bhp] British Polar Engines Ltd.-Glasgow
A bit more information regarding her cable ship conversion from a member of another "ship" site.
"Luminence" was converted for use as a cable ship when chartered to lay a duplicate set of electric power cables underneath Cook Strait, between New Zealand's North and South Islands.
I can't put an exact timeframe on that, but it would have been around 1983 / 1984.
If my memory is correct, she spent some months in NZ performing that task, and then returned to the UK.
The reason that a purpose-built cable-ship was not used was that the diameter of the power cables exceeded that of the standard telephone cables, and thus the gear fitted to a telephone cable layer was too small.
She is now the Egyptian owned, North Korean registered DREAM