Image copyright Getty Images Image caption Former politician Sergiy Tigipko is one of the most influential men in Ukraine

One of Ukraine's richest men is being investigated by Scotland Yard over the abduction of his two British grandchildren from the UK to Ukraine.

Banker and industrialist Sergiy Tigipko helped his daughter Ganna defy High Court orders to bring her children back to the UK from Kiev, a judge has ruled.

The court had ordered Ms Tigipko back to London, where the children's British father lives, so they could see him.

Sergiy and Ganna can be named after an exceptional decision by a judge.

The children were "suffering harm" by being separated from their father, the court heard.

The judge heard that publicity could make their mother and grandfather return them.

Ms Tigipko said everything she had done since her husband left her in 2015 had been "for the welfare of my children and nobody else".

She added the children were "happy and settled in Ukraine now" and that their father was "welcome to visit them".

It is believed to be the first time a judge has allowed abductors to be named in this way - usually it only happens when children's whereabouts are unknown.

Ms Tigipko met the children's father in 2010 and married in 2012.

They settled in north London, and had two daughters. But, in late 2015, the father announced the marriage was over.

Initially, Ms Tigipko was happy to stay in London. She had founded a clinic in Harley Street.

With help from her mother, she bought a £9m home in Hampstead, which is one of London's most expensive districts and popular with Russian speakers.

The children's father lived nearby with his new wife.

But then Ms Tigipko met a new partner too, and married him in 2017 in Ukraine.

In November 2017, she took the girls for a visit to Kiev - and stayed there, violating an informal agreement with the father to remain living in the UK.

She sold her house in Hampstead and gave up her Harley Street business.

In April 2018, the High Court ruled she must return to London to live - but she ignored repeated court orders.

Mr Justice Mostyn found that her father, Sergiy, had helped her.

He was fully satisfied "of his deep complicity", he said in his judgment.

As no progress was being made, the girls' father took the exceptional step of asking for the grandfather and mother to be named, hoping that would encourage them to return the children.

Image caption Mr Tigipko is being investigated by Scotland Yard

Mr Tigipko is one of the richest and most powerful men in Ukraine.

The billionaire was an ally of Ukraine's former president, Viktor Yanukovych - serving as a vice prime minister in his administration - and twice stood as a presidential candidate himself.

In recent years, he has concentrated on his business interests, and told the court he had no further interest in politics.

The court heard that before the children were taken to Kiev, they had had a close relationship with their father.

'Papa is bad'

But now they have been turned against him.

In December, the older girl told a court appointed expert: "Papa is bad."

He has three children from a previous marriage while his new wife has a son from an earlier relationship.

It is believed to be the first time a judge has named abductors in such a case.

In family courts, protecting the children's identity is paramount and they are only named when their whereabouts is unknown, as in the case of Olly Sheridan.

Mr Justice Mostyn said that he placed "great weight" on the submissions made by the barrister for the children's court-appointed guardian, who had supported publication.

He said that child abduction was a "heinous practice" and yet "public awareness is curiously very limited".

Orysia Lutsevych, from the think tank Chatham House, said many in Ukraine would be unsympathetic to the Tigipkos.

She said there was a sense that the very rich behave differently, that the rules do not apply to them, that they're "untouchable".

"I'm sure lots of Ukrainians will be watching the case," she added.