Tower, 52m, northern foot

Any suggestions where this might be? I guess it's not really that difficult to work out that it is Nelson's Column in Trafalgar Square. Tomorrow the general public will be getting the chance to orienteer around the square when Adrian Bailey spends an hour on the fourth plinth as part of the One & Other project. Helen and I have been helping to set things up so I am mapper and planner and Helen is organiser for what promises to be an interesting experience. We're still not quite sure exactly what will happen, but we have maps, control flags and SI kit so it should look like a proper race. Brooner has found an interesting publicity angle, claiming it to be the World's smallest orientering event.

You can get a sneak-preview of the map in Routegadget.

If you can't be there, don't miss the live web broadcast from 13.00 to 14.00 BST.

And that should provide a perfect warm-up for the 2009 London City Race on Saturday.