Cat Neelan

Nigel Farage is leader of UKIP.

And a brash, multi-millionaire insurance magnate from Bristol makes a big entrance to the UK political scene.

This is Michael Crick, the political journalist and author of One Party After Another, which chronicles Nigel Farage's life and early political career.

Until this point, Aaron Banks has been a Conservative supporter and donor.

His defection to UKIP is memorable.

When William Hague, then Conservative leader of the House, is asked about Aaron Banks, he dismisses him as a nobody.

Which doesn't go down well.

And Aaron Banks announces that he is now donating £1 million to UKIP.

Aaron Banks quickly becomes not just a donor to UKIP, but a close confidant of Nigel Farage.

His financial support for Brexit goes beyond the party too.

He becomes an active campaigner in the Brexit referendum, running and funding the unofficial Leave campaign, Leave.eu.

Working together with Nigel Farage, the campaign becomes a haze of stunts, billboards and slogans.

Although they're not part of the formal Brexit grouping, they can fairly claim credit for having helped to secure the result.

The British people have spoken and the answer is we're out.

But in around 2018, Aaron Banks starts to become a reputational hazard for Nigel Farage.

The Electoral Commission and the National Crime Agency launched separate investigations into Aaron Banks's finances.

Eventually, in 2019, both investigations conclude there is no evidence of any foreign interference in the loans that Aaron Banks gave to Leave.eu.

But that is some time into the future.

By late 2018, Nigel Farage is approaching a crossroads.

British politics is in a volatile place.