I'm not in general puzzled by cows, but I am when they're in a park in the middle of a city. Sure enough, every description I can find of Midsummer Common describes it as grazing or pastureland. I later found a laminated piece of paper artfully attached with zipties to the entrances to the common:
Please be aware that as from Friday 6th April 2007 the cows will be back grazing on Midsummer Common.
Initially there will be eight Red Poll steers (native rare breed cow found in the eastern region).
They will be on the common from April until October (excluding times when the events take place on Midsummer Common)
This breed of cattle is generally very calm and docile, they have no horns, and therefore are very suitable for grazing in this location.
To report any problems with cattle, please call the Street Scene help desk.
The Wikipedia entry on Midsummer Common adds that meat from the cows will be available in November. Nice. If that's indeed true, the meat won't go very far -- the cows are pretty little. Their cow patties, however, are not.
Anyway, apparently there haven't been cows grazing since the last foot-in-mouth disease scare, so it's exciting to have them back. Still, it was a bit puzzling to encounter livestock as I cut across the common. Of course, if I would have thought about it for just a minute, I would have realized that it's a mini-cattle grate that I'm bicycling over when I enter and exit the common. Duh.