The entire present day monarchy is a relatively new legal construct invented by parliament progressively following the republic stemming from the civil war. If there is sufficient public demand we can legislate the monarchy away.
The monarchy was restored on the understanding that the monarch be a mere figurehead. George III signed away any vestigial powers in return for an annual payment. He also gave up the responsibility of financing such as the army and the civil administration.
Edward VIII's position was impacted by parliament and he ended up in exile. The Wallis Simpson marriage was not acceptable.
In recent times parliament has made it possible for the first born to be monarch even if female rather than male precedence as was.
The royals and PM's sniff the wind. The pressure will not be end of monarchy but fewer of them doing public duties for which they get a stipend. Fewer on the balcony and smaller group photos.
Unlike the Netherlands I doubt we will see a king or queen going round on a bike and shopping in Waitrose....
As was drummed into me at school. The monarch reigns but parliament governs. If we wanted it we could have a republic with no violence at all....save like Brexit amongst ourselves...Just like the civil war, cavaliers v roundheads etc....