Ghost Signs & Shopfronts is seventy-five minutes and £12, and it runs on Thursday evenings from May to September because it needs low sun to work — the painted advertisements on the gable ends only come back at about seven o’clock. Isla leads it with a folder of photographs taken between 1898 and 1961, held up against the wall you are looking at, and it is the walk people book twice. Beyond the public timetable, a private walk is £180 for up to twenty people on any route and any date we are free, which covers birthdays, wedding parties on the Friday before, and firms bringing new staff into the town. Bespoke routes cost the same £180 but need a fortnight, because a new subject means a day in the record office and we would rather do that than improvise. Subjects we have built and would happily run again: the Civil War siege of 1645, the flood defences and what they replaced, the Victorian shopfronts of Mardol, the workhouse and the people in it, and — twice, by request — the entire history of the town’s drains, which was startlingly popular. School half-days are £240 for up to thirty-two pupils with two guides and a pack of copied documents the class can handle.

Every ticket includes a qualified guide, a route built from primary sources, and the documents — photographed, printed or held up on a phone — that the guide is quoting from. You get a printed card at the end listing what we mentioned and where to read more, because a fifth of the people on any walk want to go further and it is rude to send them away empty-handed. Under-fives go free on every walk; under-sixteens pay the concession rate. What the walk asks of you is comfortable shoes and ninety minutes of standing and moving — the Shuts route is a mile and a quarter with six proper stops, but Wyle Cop is genuinely steep and two of the passages have worn steps without handrails. We run a step-free version of that route which adds two hundred yards, misses one stop and gains a better view of the river; ask for it when you book rather than on the morning, and Isla will confirm the adjusted route in writing. There is no minimum number: we have run a public walk for two people in February and we did not shorten it.