25.5.1794 Walker calls (after Smith breakfasts) / 1.6.1794 again / 15.6.1794 again / 4.10.1794 at Powell's (with Roberts) / 1.11.1794 at Hardy's trial (with Roberts M) / 23.11.1794 calls (after Smith breakfasts) / 7.12.1794 again / 20.12.1794 at Powell's (with Roberts) / 17.1.1795 at Powell's (with Thelwall, Bailey, Manning, Lee) / 31.1.1795 again (plus G Richter) / 2.2.1795 at Thelwall's (with Bailey & G Richter) / 7.2.1795 at Powell's (with Lee) / 14.2.1795  at Powell's (with Manning & Lee) / 12.3.1795 adv at Gerald's / 21.4.1795 at Anderson's / 3.5.1795 at Tooke's / 4.5.1795 to theatre with Godwin (uncoded in GD website) / 24.5.1795 adv on Godwin's walk to Putney / 12.6.1795 at Thelwall's (after lecture, with Richters & Mannings) / 27.5.1798 at Tooke's / 29.7.1798 again / 10.2.1800 Walker adv at theatre / 15.1.1801 Keir & Walker call (not in) / 9.5.1801 Northcote sups (Lyrical ballads); adv Walker; talk of Pope, Rembrandt Rubens & Raffaele / 20.5.1801 Northcote & Walker sup / 22.5.1801 Walker sups / 2.6.1801 again / 14.6.1801 Northcote & Walker sup / 15.6.1801 Walker & M(arshall) dine / 18.6.1801 Walker at tea / 28.6.1801 Walker adv at Nicholson's / 31.8.1802 write to Johnson, on Walker / 8.11.1802 Walker calls (not in)
All the above Walkers could be one person, more especially the 1794 and 1795 entries. See Walker, Alexander for Walkers from 1800, some of the entries above could have been him. Walkers earlier in Godwin's diary were John Walker, Walker goldsmith, G Walker (see my website for these three) and Thomas Walker of Manchester (see GD website), there's no reason to think the Walker(s) above was any of those. This Walker began, like Richard Johnson the year before, by calling on Sunday mornings, 5 times in all, perhaps to enjoy the tail end of Godwin's Sunday breakfast discussions with Smith. He also went 6 times to James Powell's and twice to John Thelwall's in similar company, which circles are the closest Godwin got to the London Corresponding Society world; and Hardy's trial, Gerald's prison and Horne Tooke's were all appropriate venues for someone with those interests.
Possibles were William Walker, son of the scientific lecturer Adam Walker DND 1730/1-1821 (the William Walker who entered New College, Hackney in Sept 1787?), two 1801 entries, one with Keir and one at Nicholson's, might suit father or son (see my entry for Walker, Adam in Society for Constitutional Information dataset) / David Walker, bookseller, and (if he was the same David W) journalist for the Gazetteer (Nat Arch C104/67 & 68). Signatories to the 1792 Declaration of Friends to Liberty of Press (which covered a wide range of SCI & LCS members as well as others of broad liberal sympathies) included a David Walker and a Theophilus Walker. A Richard Walker and a Thomas Walker each subscribed 3 guineas, through Daniel Isaac Eaton, to the LCS collection for the families of state prisoners in Nov 1794, & J Walker of Aylesbury St & Walker of Harcourt Bldgs Temple both subscribed to Winterbotham's America 1795 (while the author was in Newgate)

Work notes: 
Law List 1794 Edmund W 2 Serjeants Inn, clerk to Sir Beaumont Hotham, Baron of the Exchequer / Wm W Esq 5 Kings Bench Walk, Inner Temple, counsel / Charles W Esq 3 Lincolns Inn Old sq special pleader / Wm W attorney Leicester Pl Leicester Sq & 14 Buckingham St, York Bldgs / Charles W attorney 20 Cateaton St or at Mr Thomas Arnold Loxley's office, Poultry Compter, clerk sitter