My regulator is investigating a concern which I have already been notified of

Once the regulator has your initial response to the concerns they will then gather further evidence to enable them to decide whether there is a case to answer. If the case does proceed then this evidence will be put before the panel in support of the regulator’s case.

The regulator does not have a duty to investigate on your behalf or to collect evidence just because you ask them to.

Technically during this phase you do not need to do anything as it is the regulator’s responsibility to build their case against you and no decision will have been reached as to whether the case will in fact proceed. However, in reality it makes sense to try to secure any evidence that you think might support your defence, if the case is eventually heard by a panel. Bear in mind that depending on the regulator it can be many months – sometimes years – between the concern being raised and it actually going to a hearing. This might mean that by the time it comes to preparing for a hearing, you have lost touch with former colleagues, or do not have access to emails, correspondence or other evidence.

A lawyer will be able to help you understand what sort of evidence you might wish to collect. They can also help by taking witness statements from anyone you want to give evidence, or in complex cases, an expert who might be able to give technical evidence to explain normal procedure, professional standards or the complexities of a particular medical condition.
If the concerns relate to a point in your life where you were suffering from a medical condition, including stress and mental health issues, or experiencing employment issues such as bullying or harassment then it is advisable to gather as much evidence as you can, in case it does form an important part of your defence.