I found this lovely on my living room ceiling. It is a species of running crab spider, and a male, and oh boy do they run fast!
It is normally found on the lower branches of trees and shrubs in wooded areas, but it is also found in gardens and occasionally indoors. The sexes vary quite differently, hence the scientific name. It is quite common in Southern Britain.
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May 2018, photos taken in rear garden, Staffordshire, England. © Pete Hillman