A spokesperson for the board said it was undertaking a ‘comprehensive and robust review of theatres' at the University of Wales following issues raised through an internal staff survey.

The board said the review was taking longer than the anticipated 12-16 weeks due to the ‘significant contribution of colleagues'.

The spokesperson added the review had identified ‘previous concerns regarding unauthorised people in theatres had been raised but not thoroughly investigated or completed'.

‘Following these deeply concerning allegations made, we have launched an internal investigation,' the spokesperson added.

‘This investigation has yet to reach its conclusion but will be conducted and reported to the board as per the health board's process. We continue to actively encourage all colleagues to raise any concerns and this has also been a focus for further improvement and development across the health board for some time.'