London Banter - Can you identify this train?

All,

My parents were on holiday near Carlisle last week, and saw a train,
the description of which I cannot place.

The facts as relayed to me a

* seen two days running (Monday 4 and Tuesday 5?) passing through
Carlisle at about 1100
* heading south
* hauling containers (or empty container flats)
* class 66?
* loco livery had "lots of white"
* apparent operator name was something like "Open Freight"

Now, my father sometimes remembers things incorrectly, like the person
wearing blue uniform that he "remembered" as wearing white, so the
last two items may be red herrings. However, the sight was
sufficiently out of the ordinary for him to bother to tell me about
it.

But... what was it? I tried suggesting some names (Colas, DRS, the
Tesco/Stobart liveried loco, Fertis (yes, highly unlikely I know!),
Cotswold Rail), none of which triggered "that must be it" responses.

Any thoughts, anyone? What was the loco livery, and who was it
working for (if not self explanatory)?

Thanks

PhilD

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