Common Darter (Sympetrum striolatum)
Although one of the more common Dragonfly in the UK, this elderly female, was a fine example of how variable life cycle colour changes can temporarily throw you when trying to ID a species.
This is particularly applicable to Odonata, which have enough colour variables as it is.
Short video and additional info here:

The Common Darter is a dragonfly of the family Libellulidae native to Eurasia. It is one of the most common dragonflies in Europe, occurring in a wide variety of water bodies, though with a preference for breeding in still water such as ponds and lakes. In the south of its range adults are on the wing all year round.