Yes, it would be good to know exactly what the Brexiteers think they have achieved by this. It strikes me that all they have really achieved is delays for pretty much everyone at the borders coming either in or out though, to be fair, for passengers that is as much Covid-19 as anything, not so for freight. I don't think it has or will affect the arrival of illegal immigrants and refugees though the French might not give us so much assistance in the future. As for the Eastern Europeans, I guess it will prevent the less skilled from coming in but I am not sure that they much want to much now. In many cases these are the seasonal workers that we actually need to harvest our crops so that isn't really any sort of benefit anyway.
As for what else might be considered a 'sovereignty' success: we have our fishing rights back within our Exclusive Economic Zone (EEZ). Oh wait, we don't but we have at least stopped the fish caught in British waters for export at the borders; obviously it is better that they rot at the sovereign border posts than are sold for a profit and consumed beyond our borders. British fish for British people! We have certainly prevented goods that are manufactured here from parts bought in from overseas from getting out, ditto similar products from the EU now can't get in: British goods for British people too! What else? We can stop horrid old EU citizens from coming in and using our health system, I suppose, as they wouldn't get enough points to qualify; as for our own EU expats living happily in Spain and not costing our health care system anything, I guess they take their chances. Even if they come back they would no longer be entitled to health care anyway so that should save some money! Bottom line - sovereignty means that we can treat EU citizens as the foreigners they are and, because we are British, we can enjoy being foreigners again in the EU! Win - win I say.
As a footnote, prior to our leaving a popular line amongst the more rabid of Brexiteers on the BBC's HYS which, Katharine, I suspect you might read occasionally was to accuse we so-called Remoaners of being unpatriotic. I was fortunate enough to have had dealings with large numbers of World War 2 veterans over the years and I can categorically say that the vast majority of these people, who were real patriots even if they might have raised eyebrows at the term, were firmly in favour of the EU and European integration. Did Captain Sir Tom ever express a view on this do you know?