HMRC would expect that someone who is being described as a competent professional to be knowledgeable about the relevant scientific and technological principles involved, be aware of the current state of knowledge, and have accumulated experience and be recognised as having a successful track record.
This person is likely to be a lead developer or engineer. This person will be best placed to asses which of your projects will count as R&D and to provide the relevant details to enable technical reports to be written.