I've been thinking a little about the logistics of Sunday Lunch and Sunday Walks. If you go for a walk in the morning to build up an appetite, return home and then have a proper roast Sunday lunch, either someone needs to be at home to cook, or you're an hour and a half minimum from eating on your arrival. Hence the walking to a pub for lunch.
If you're walking after lunch (to burn off all that stuff you've just eaten) choosing a pub near an interesting walk again saves you valuable time and, in the winter, daylight. People living near interesting walks can avoid this problem. One final note - it's due to the lack of daylight on Winter Sunday's that my family tend to eat the main meal in the evening; otherwise Sunday Lunch eats up the entire day.
 In Summer you could barbecue; you really need to let charcoal burn for at least half an hour before cooking on it anyway, but some sort of cold starter could easily take up the required time.