Maybe that's the case at Biggin (never been there to see) but civil IFR where airfields where I have worked have edge lights which have bi-directional high intensity lenses in a 'dome' which gives a low intensity omni-directional element and VFR airfields have just low intensity omni-directional lights, both types of light being spaced at 60m intervals.
When the airfield where I worked still had a 'military' lighting system, the edge lights were high intensity uni-directional, back to back to serve both runway directions spaced every 30m with a low intensity omni directional light every 90m, the HI and LI lights being controlled separately so you could have the HIs set as per your lighting chart and the LIs on full blast for circling guidance.