The idea that proroguing Parliament is 'normal' as this government has done it is simply not credulous. It is an anti-democratic move, and it should be no surprise that the government is also considering not handing legislation passed by Parliament to the Monarch to sign into law.
This all blows the notion that somehow the Monarch is a protector of the unwritten constitution into the wind. The Monarch only ever does what the Prime Minister says, and this inheritance gives a Prime Minister enormous power. What usually stops a Prime Minister from abuse of power is convention.
There are two identified types of convention. One is ordinary and the other is embedded. The difference, Professor Vernon Bogdanor has told us, has never been defined. Nevertheless, proroguing Parliament in this devious manner is a convention, and likely to be regarded as politically unacceptable but legal. For a government to fail to send legislation to be signed by the monarch would flout an embedded convention, and the Supreme Court would stop it.
In any case, should the Fixed-term Parliaments Act run out of time in terms of having an emergency government (say headed by Harriet Harman or Yvette Cooper) because of proroguing, and/ or Johnson in power, then Johnson may call a General Election for after October 31st.
In this case there are two options. One is that noting the voting the European Union unilaterally extends Article 50 and then, to keep trade and people flowing, a new government legislates retrospectively. Alternatively a new government uses Article 49 and legislates retrospectively.
Being anti-democratic in a democracy run by conventions is a dangerous move. I think this is enough to have its perpetrator dismissed from office by anyone of liberal democratic sympathy.