Judging by the recruitment of staff in this advert they recruited many staff in all aspects of making and altering clothes as Audrie mentions. This was prior to Audrie’s employment, but gives an idea of the staff they needed: milliners, tailors, tailoresses, dressmakers and alterations hands. So a strong skilled workforce doing much more than alteration work. Must have been a fascinating place to work (well to me). I expect as more customers moved towards ‘off the peg’ items, the need for a full tailoring and dressmaking service must have declined.
I also wondered if they hand-made wedding dresses. I can imagine brides being very proud to say they had their wedding dress exclusively made at Marshall and Snelgrove.
In time off-the-peg clothes must have really taken hold as ‘a shop within a shop’ enterprises became common, like the Cresta shop within Marshall and Snelgrove - advert below. By the 1960s they had their own fitters and alteration hands.
Eventually these in house shops must have effectively turned departmental stores into conglomerates of concession stores, like Rackhams and Harrod’s stores. But even they have struggled to survive, very few still exist.