As the sun is currently shining more and more, I would like to turn your attention to Para No. 0129/0130 of AP1358C in regards to wearing sunglasses:
(Paraphrased for easy read - look at the AP if you want to look into this further)
Occasions for Wear:
On health and safety grounds, suitable civilian purchased sunglasses may be worn with uniform, outdoors, both in UK and overseas. On all other occasions discretion to be used by OC Wg / Wg Ex O / CCF CC.
Non-prescription sunglasses are not to be worn on parade / formal occasions unless specifically authorised.
They are to be unobtrusive in style and neither eccentric nor “eye catching”.
Frames are to be of standard style and colour; bright or multi-coloured frames are not permitted.
Lenses are not to be mirrored and are to be of a dark colour similar to the Service issue.