Labour 38% (+3)
Liberal Democrats 10% (+1)
SNP / Plaid Cymru 5% (n/c)
UKIP 4% (+1)
Greens 1% (-1)
To answer the question a lot of people are asking : yes, if there's a uniform swing between Tory and Labour, and if the Lib Dems and SNP are resilient in seats they're defending, this poll takes us firmly into hung parliament territory. The trouble is that the Brexit factor means there almost certainly isn't going to be anything even close to a uniform swing, meaning it's impossible to know for sure whether a 5% Tory lead would translate into a hung parliament or a small overall Tory majority. But at the very least it would put the Tory majority at severe risk.
Of course the million dollar question is whether the polls are even accurate. It would be a mistake to jump to the conclusion that the polls must be underestimating the Tory lead by roughly as much as they did last time, because methodology has been changed since then in the hope of avoiding any repeat. Nevertheless, Matt Singh is gaining a lot of publicity for his prediction that the Tories will once again significantly out-perform the polls. I must say I was a little underwhelmed by his reasoning - he's certainly on solid ground in suggesting that leadership ratings are predictive of election results, but I fear he may be placing too much emphasis on the sharp difference between the outcomes of May local elections and June general elections in 1983 and 1987. It's possible there were 'era-specific' explanations for that phenomenon (such as the existence of the SDP-Liberal Alliance). There's no reason to automatically assume that because something has happened twice in the relatively distant past, it's bound to happen a third time.
And a comforting thought to finish with - if this poll is close to being right, it reflects the state of public opinion at a time when the election was already underway. A great many postal votes have already been cast.