Overseas readers should be in no doubt. Brexit is now a policy that is as certain as anything can be in politics.
Within a short period of time, the United Kingdom will have a new Prime Minister with the backing of her Party. Theresa May, highly experienced and intelligent, has made a public commitment to see Brexit through without the disruption of a General Election that would take opportunistic advantage of the disarray elsewhere in the political system. She will have to confirm her mandate with the people but not immediately, almost certainly when Brexit is irreversible.
The instabilities in British political life are now no longer at the centre of things but moving out towards the periphery. Even serious issues like the Scots commitment to the Union and the possibility of a border being reimposed between Northern Ireland and Ireland are now just standard problems for a stabilised centre to resolve. They were never going to be deal-breakers on Brexit. The further away one is from London, the more likely that Remainers will be in denial but most have long since moved on to anger or depression or even, the final stage of grief, acceptance.
Two forces not currently in power are currently undergoing major internal realignments. Both bear close watching. The first is the Labour Party, the main party of opposition and government since the 1920s, and the second is UKIP, barely a quarter of a century old, whose purpose comes into question once the Brexit process has been completed. UKIP is the easier case. Either a new Leader constructs an ideology of working and lower middle class national patriotism that ouflanks the Tory Party by challenging Labour or it sinks into marginality - or, worse, the ghetto of the far right.
UKIP is now a player (assuming no backsliding on the part of Theresa May or a Remain revolt on the Tory backbenches) if and only if it can present a distinctive populist ideology that appears to serve working class and middle class interests better than the Government (which should be relatively easy) but also better than the Labour Party. Labour is currently giving UKIP a clear shot at goal by allowing its professional politicians to challenge a popular anti-austerity and anti-war Leader only days after that Leader was proved prescient (following the Chilcot Report) on the Iraq War.
Angela Eagle's challenge to Jeremy Corbyn operates at multiple levels of political meaning but three stand out. It is the use of the soft Left as 'front' for the Right in the preservation of Labour values centred on Parliamentary capture of the State. It is the continuation of the most sustained historic struggle in the Labour Party - not between Right and Left but within the Labour Left itself, something we personally witnessed on both sides of the divide in the mid-1990s. It will decide whether Labour will challenge the Tories as the Party of the People or as an alternative Party of the State.
Theresa May has worked fast to pre-empt the potential challenges from both parties by taking an unequivocal line on Brexit (responses to Brexit are part of the subtle differences between the Hard Left and the other warring Labour factions) and introducing a startling workerist agenda of her own for the Conservative Party, much to the consternation of the City. What we have to watch for is not so much divisions over Brexit but what sort of opposition the Government will face over the next few years - populist and campaigning, conventional and Parliamentary or divided and fractious.