Nigel Farage has said that Brexit is an “incredible victory for ordinary people against the establishment”.
As the UK prepares to leave the European Union later on Friday, the Brexit Party leader warned that Britain will never return to the EU after it leaves at 11pm tonight.
Mr Farage’s comments came a day after he unveiled a portrait of himself to raise money for charity.
In an interview with Good Morning Britain, Mr Farage said: “There's lots of work to come, but think of this, what happens tonight at 11 o'clock, we pass the point of no return.”
He added: “Once we're out, there's no way this country will ever rejoin.
“I think this is the big moment in history.”
Mr Farage also praised prime minister Boris Johnson, whose landslide general election win in December finally paved the way for Brexit.
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“As for the next phase, all I can say is right now, Boris Johnson is saying all the right things and if he delivers those things, we will be truly, genuinely independent,” said Mr Farage.
“I have to be honest, I'm feeling really optimistic.”
Mr Farage also took to Twitter to express his mood.
He tweeted: “Happy Brexit Day!”
He also wrote: “At last the day comes when we break free. A massive victory for the people against the establishment.”
As 11pm arrives, Big Ben will remain silent, despite a high-profile campaign fuelled by Mr Johnson for repair works to be halted to allow Parliament's bell to ring.
But on Parliament Square, Brexiteers will gather for a party led by Mr Farage, while Union flags are already flying around Westminster.
In official events, Downing Street will be illuminated with a light show and a new 50p coin will enter circulation.
In Brussels, the UK flag will be removed from the EU institutions, with one Union flag expected to be consigned to a museum.