That should read "Some Garratts", perhaps even "Most Garratts" but Derby did insist on the standard midland 8' +8'6" wheelbase, and since the whole railway was built to suit locos with that wheelbase it was not an issue for them.
Incidentally, not such a big size difference between a GMAM and an LMS Garratt, the GMAM was some way off the SAR's biggest.
Loco length weight cylinders boiler dia TE
LMS Garratt 87'10" 155.5 18.5 x 26 6'9" 40250
SAR GMAM 95' # 191.75 20.5 x 26 7'0" 60700 #dimension from RR 20th class, will be the same within a few inches
EAR 59 class 251.68 20.5 x 28 7'6" 73500
Great photo Alastair
Keith