The purpose of the Act was not to block a no deal Brexit. It was to provide additional time to negotiate a deal (this is what it says) - which has been done. The extension is available only to negotiate a particular type of deal - eg the Kinnock Amendment.

I don't doubt the Courts would probably 'interpret it widely' but that is improper - it is not for the Courts to ignore or re-write what is clearly set out in the legislation. The meaning here is quite clear - Parliament could have rejected the Kinnock Amendment if they did not intend this limitation. One of the consequences of Brexit has been to expose the falling standards in the Court system.

Only if the extension is for the purposes set out in the Act. You can't just ignore clauses in legislation that you don't like.

Wrong. The Act says the extension is required "in order to debate and pass a Bill ... including provisions reflecting the outcome of inter-party talks as announced by the Prime Minister on 21 May 2019, and in particular the need for the United Kingdom to secure changes to the political declaration to reflect the outcome of those inter-party talks."

If the extension is not for this purpose the PM does not need to accept.

You need to read the text of the Benn Act. That is not what it says.

Boris can reject any extension under the Benn Act. Any extension has to be for the purpose of the Kinnock Amendment. Technically illegal for Boris to accept an extension to pass his deal later since to do so would be contrary to the provisions of the Benn Act.

If Boris was going this way:

(a) he would say he was still leaving on 31 Oct (he just did)
(b) He would comply with the Benn Act by inviting the EU to offer an extension in response to the Benn Act before rejecting it (he just did).

They could pass a new bill, but they are running out of time. The QS debate has not concluded and obviously there is the WAIB to do now - it would be remarkable if they were to hold up all that just to pass a new bill about the extension.

The wording of the Benn Act is "The Prime Minister must seek to obtain from the European Council an extension ... in order to debate and pass a Bill to implement the agreement between the United Kingdom and the European Union under Article 50(2) of the Treaty on European Union, including provisions reflecting the outcome of inter-party talks as announced by the Prime Minister on 21 May 2019, and in particular the need for the United Kingdom to secure changes to the political declaration to reflect the outcome of those inter-party talks." I think that is clearly incompatible with obtaining an extension to pass Boris' deal. Boris would be entitled to refuse any extension offered in response to the Benn Act unless it specifies that it is for the purpose of the Kinnock Amendment.

Yes, it has always been impossible for the HoC to replace a PM without calling an election if the PM does not resign. When Thatcher passed a VONC in Callaghan he did not resign and was PM until the day after the election. There is nothing in the FTPA that changes that position.

I think Boris has been 'lawyered' to death. The moment Cox and co lost at the UKSC they were not interested in doing anything else that might lead to another defeat - anyone who has even engaged counsel knows that ultimately they are far more interested in their own interests and reputation than their client.

Boris had multiple options to challenge the Benn Act but has refused to follow through. As you say, he could have blocked the Benn Act by blocking the Lords. But I think the constant whispering of lawyers in his ears has undermined his confidence.

The Cabinet Manual is not law, nor is it convention. It is written by civil servants. The PM can reasonably claim that, in his view, no stable and enduring Government can evolve from the House, or that it would be unreasonable because such a Government would have no electoral mandate. This is especially true since the convention is that the LOTO is invited to become PM precisely because he has an electoral mandate to form a Govt if the existing Govt falls. This does not apply to a 'unity' candidate who has never stood for election on any platform of Government.

Ultimately, HM acts on the advice of the PM. As it says clearly, "what occurs during the 14-day period is matter of politics and not procedure." And as a result, the PM can stay and the UKSC cannot intervene.

The Letwin amendment does not do what many people on this board claim. It does not keep open an extension until after the WAIB is passed. It cannot do that, since that would require a change to the Surrender Act legislation and a mere motion cannot substitute for legislation.

In fact, Boris can easily avoid the Surrender Act now:

1. If the 2nd reading of the WAIB passes, he can use this to satisfy S1.5 and S 1(1)(a) of the Surrender Act and withdraw the extension request. The Act simply says that a 'resolution' needs to be passed proposed by a 'Minister of the Crown' - which is exactly what passing the 2nd reading would accomplish.
2. In any event, Boris can refuse any extension offered by the EU. The Kinnock Amendment (1.4) is now relevant because there is a deal. Any extension has to be granted for the specific purpose of pursuing a WA that complies with the Kinnock Amendment. Since the WA does not comply with the amendment, the EU would basically have to declare that to provide an extension they want to tear up Boris' deal. They will not do so. Therefore Boris can decline any extension on the grounds that it does not comply with S1.4 of the Surrender Act. He would be able to argue that in fact it would be illegal for him to accept an extension whose objective was to pass his deal at a later date.

The question is whether No 10 are serious about leaving the EU on 31 Oct, not whether they are able to do so.