Image copyright AFP/Getty Image caption Vote Leave was the official campaign to leave the EU

The architect of the Vote Leave campaign says it is possible last year's Brexit vote could turn out to have been an "error".

Ex-campaign director Dominic Cummings said "lots" of things could happen to make him wish his side had lost.

But he also stressed there were more possible outcomes in which leaving would be good for the EU and the UK.

Mr Cummings made the comments in a Twitter exchange with legal commentator David Allen Green.

He tweeted (his Twitter name is @odysseanproject) that there were "more possible branches of future" in which leaving was "a good thing", saying it increased Europe's "overall ability to adapt more effectively to an uncertain world".

Mr Cummings also warned Brexit negotiations were heading for a "debacle" without "management changes" in Downing Street, although he said warned the importance of the talks was "greatly overstated" compared with domestic reforms that could be carried out.

"Decisions re our own institutions will decide success/failure," he tweeted.

Critics, including pro-Remain Lib Dem leader Tim Farron, seized on his comments.

The UK is due to leave the EU in March 2019, and formal negotiations between the two sides have started.

Earlier former Tory chancellor Nigel Lawson, who campaigned to leave the EU, predicted a £10bn "Brexit dividend" for the UK once it leaves, describing this as a "great chink of light" for current Chancellor Philip Hammond.

"Once we leave there will be this £10bn a year bonus - unless we are foolish enough to negotiate it away," he told BBC Radio 4's Today programme.

Leave campaigners have previously cited a £32bn "dividend" in the three years after Brexit, calculated by adding together the UK's net contribution for each year.

The issue of any "divorce bill" the UK might face is expected to be tackled at an early stage of the talks.

Before the negotiations started, the government set out its negotiation aims, including a new "comprehensive" free trade deal with the EU.

Another former chancellor, Labour's Alistair Darling - who campaigned to stay in the EU - said the UK looks "pretty clueless" as it attempts to negotiate its way out.

Image copyright PA Image caption Nigel Lawson unveils the 1989 Budget...

Image copyright Getty Images Image caption ...And Alistair Darling presents his in 2010

Lord Darling, whose stark economic warnings before the Brexit vote have not yet materialised, said: "Until we know what the Brexit settlement is, and frankly at the moment we haven't a clue what it is - and every day the government is giving an impression that it hasn't a clue either what it's going to look like - you won't know what the economy is going to do."

He added: "Here we are, shaping the future... and the UK looks pretty clueless at the moment - I don't ever recall a situation where our country has been in that position before."