Removing things...
Insert suitable starry-bolt removal thingy into starry-bolt and undo. Anti-clockwise, should do it.
Try not to lose over summer.
PS There may be some other bolty things, too. If so, take them off. But don't get carried away; some of them are important.
PPPS Have you considered the dreadful effect when you go off-roading in an adventure-styleeee way, bash your brake lever on a tree and catapult yourself over the handle bars? Don't go off road? It can happen in Lidl car park, too. Take care.