Geranium molle. Today's theme, wild flowers. Like most parks hereabouts, they take a less managed approach to areas, regularly leaving swathes unmowed and unmanicured and not just in May. Long grasses, nettles and cow parsley line the moat and through the railings these tiny flowers were pushing through. I thought they were some kind of geranium and used that traditional ID method, Google Lens, to work out which. Really should get the proper spotter books out.
I've mentioned this blog before but if you're interested in nature in an urban situation try https://bugwomanlondon.com/. She has a regular Wednesday Weed feature which is great for shining a light on just these sorts of urban survivors.
A complete change of plan in town gardens thank goodness. I was never a fan of bedding plants in all their regimented lines. A bit if natural growth is much prettier & good for wild life.