(This article was written by Ian Gilliver and is reproduced from Issue 56 of Lokation, the London Orienteering Klubb newsletter.)  

LOK achieved a world first at Chislehurst Caves on the evening of Saturday 19 September 1987: the world's first day-time night orienteering event, or more simply, the world's first underground orienteering event. One hundred and one competitors accepted this unique navigational challenge and some twenty more pursued the less taxing wayfarers course.

The intrepid navigators completed a testing course some 2.5km in length and comprising 22 controls. Winner by a clear minute was Jim Mallinson in little over 25 minutes - not bad for a course with seven sets of master maps. The slowest competitor took more than four times that long.

The caves were formed by human excavation of a chalky hillside. The terrain was essentially flat, cool and gloomy. There were some similarities to a street event, except the streets had no names. Imagine dark grey-walled terraces of parallel or near parallel streets, crossed nearly at right angles with more of the same to form small blocks of buildings, each looking the same as the next. The surface of the streets is uneven, possessing a cobbled quality. Occasionally you would clamber over a pile of earth, obstructing progress down the street, and occasionally you would see a disused toilet block. These latter date from the Second World War when the caves were used as an underground shelter. One competitor showed Hazel Blackstone the bay where as an evacuee he had slept more than 40 years earlier.