On this basis, the OP will now never be able to visit a museum in London or attend a professional football match in England or Wales.

The fact is that high profile buildings and events are potential terrorist targets. It’s possible to build a device that would cause considerable damage in something small and seemingly insignificant that would easily fit in a bag or coat pocket. X-rays and/or bag searches are a proportionate response to the risk - what is more important is that the security personnel are trained to recognise explosive devices, not that we are held up for a few seconds.