This is in the mini-'piazza' between the Ashton Memorial (the porch of which provided this viewpoint) and the Butterfly House in the background.
The design combines the city's crest with the county emblem, the Red Rose of Lancaster. The style, combining natural cobblestones and cut inserts, strongly resembles that used in the Wray Millennium Mosaic, so I guessed correctly that it's by Maggy Howarth (not 'Maggie').