This is one of many urban trails within Greater London, with good access points via transit. It loosely follows the river Pinn through a range of terrain - road, gravel/dirt and paved paths, and grassy fields - with occasional forested pieces. The path is almost entirely flat, though be mindful of the varied terrain when choosing your footwear. Outside of particularly wintery (like today) or wet conditions, the route distance and terrain would be appropriate for all levels of runners.
Specific to today's run:
1) This month has been cold for the area, so the route was uncharacteristically snowy through the fields and had several long stretches of icy hard-packed snow as well. Within days, the snow will melt and the route could likely go 10 minutes faster.
2) There is a construction detour (not weather-related) at approx. mile 4 that takes you onto the road around a closed portion of the grassy waterside paths, adding ~0.3mi to the traditional route. This small detour could be in place for some time.