A union boss was attacked after speaking at a counter-protest to a rally supporting jailed far-right leader Tommy Robinson and US president Donald Trump.

Steve Hedley, senior assistant general secretary of the RMT, was assaulted by supporters of the US president and Robinson, according to anti-fascism campaigners Hope Not Hate.

It came as Scotland Yard confirmed that 12 people had been arrested at the demonstration for offences ranging from violent disorder to assault.

Witnesses said a mob ambushed two men at the Westminster Arms pub in central London in a targeted attack.

"They (the attackers) knew what they were doing," one witness, who asked not to be named, said.

Smashed glass was strewn across the pavement outside the establishment on Storey's Gate, and pictures showed Mr Hedley with a bandaged head and bloodied face.

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A number of violent clashes broke out as police officers attempted to keep the demonstration under control on Saturday afternoon.

Police had feared violence ahead of the rally in support of Mr Trump and 35-year-old Robinson, who was jailed for 13 months for contempt of court after filming people involved in a criminal trial and broadcasting the footage on social media.

The march to Downing Street was kept at a distance from the counter-protest in Parliament Square, the day after an estimated 250,000 rallied through London in opposition to the US president.

Mr Hedley was among those to speak at the counter-protest.

Some outside Downing Street waved "Britain Loves Trump" placards, wore Mr Trump's red Make America Great Again caps and cheered at mentions of the US leader, but the main focus was Robinson.

Police said Trump supporters were due to leave the US Embassy and meet Robinson fans on the way to Whitehall, but ordered both must depart Temple Place and follow a strict route after "serious violence" at a march last month resulted in five officers being injured.

Pictures on social media showed a small group breached the order by starting at the US Embassy. Officers at the scene said cordons had been bolstered after the breaches.

The Met could not immediately comment on Mr Hedley's attack.

Additional reporting by Press Association