Leigh leaves Westpac New Zealand Ltd, where he has spent four years as CFO, to take up the role at the bank, which is being created from the sale by RBS of around 300 branches and other business banking elements.
Prior to his time with Westpac, Leigh held senior UK banking and corporate finance roles with RBS, Alliance & Leicester, PwC and KPMG.
Leigh will join Williams & Glyn on 1 September, subject to regulatory approval.
Commenting on his appointment, Leigh said,
"I'm very excited to be taking up this position and I look forward to playing a leading role in building a vibrant UK challenger bank in Williams & Glyn. Williams & Glyn has a proud heritage of customer service, which reaches back to the 1700s. The new bank will draw on this and be a positive and powerful addition to the UK banking sector."
Commenting on the appointment, RBS Chief Administrative Officer, Simon McNamara said,
"I'm delighted to welcome Leigh to the Williams & Glyn team. He brings with him a wealth of expertise and experience, from both here and abroad. He will play a key role as we move towards the launch of Williams & Glyn next year."