Allocations of GN express locos

[kudu]

Challenger Publications have produced an interesting tabulation of LNER loco allocations on "The First Day" - 1/1/1923. I have been looking at the distribution of GNR Pacifics (all two of them), Atlantics, 4-4-0s and 2-6-0s, all of which handled GN expresses (some as pilots) but also express freights.

Overall, 17 of the 19 GN sheds listed had at least two of these types, exceptions being Hornsey and Trafford Park. Perhaps the oddest feature to me is the paltry allocation of these locos to Copley Hill, confined to 11 4-4-0s. This raises the questions of what classes typically covered the London expresses, and where were they allocated in the last days of the GNR.Were engine changes involved? Another shed with a meagre allocation was York, a small shed but a key location in pre-Grouping days. York also had 11 4-4-0s, plus 3 Klondyke Atlantics.

By contrast Doncaster had a total 70 of these four types, more than any other shed, including 29 Atlantics. Given that none would work beyond York I wonder what duties they covered. Doncaster also had the two Pacifics plus 17 4-4-0s and 22 Moguls. Second only to Doncaster, New England had 65 of these types, 33 of them 2-6-0s and 29 Atlantics. Only 3 were 4-4-0s, perhaps a surprisingly low number given the secondary routes to Boston and Lincoln.
With all those Atlantics, am I right to assume Peterborough was a loco change point as an alternative to Grantham (which had 30 Atlantics)?

Any clarification would be welcome, especially on the Kings X - Leeds service and on what Doncaster did with all those Atlantics in the later days of the GNR.

Kudu

[Hatfield Shed]

For comparison RCTS GN loco history vol 3A. On 31st Dec 1922, the allocations of small / large atlantics:
London KX: 4 / 20
Peterboro' 11 / 18
Grantham 0 / 31
Doncaster 4 / 25
York 3 / 0

The superheated piston valve large atlantics were concentrated at KX, as by then there was through working KX - Doncaster - Leeds, and the KX allocation of small atlantics were wholly or in part (text ambiguous) sub-shedded at Cambridge.

The large atlantics at KX I believe usually came off at Peterboro' or Grantham on York services, but worked through to Leeds. Someone with superior knowledge can put me right if that's not right or a sweeping simplification...

[kudu]

Belated thanks for your response. I wasn't sure what the arrangements were on the Leeds services. It remains odd that Copley Hill had no express locos back then.

Kudu