If people were to produce legal documents while under illegitimate pressure to do so, then they might later be able to challenge the arrangement based on that pressure – see [taking legal advice] for a fuller explanation (from the other perspective). Most people would wish to avoid the possible cost and uncertainty entailed.
Someone instigating the production of legal documents by anyone else may wish to minimise the possibility of a later challenge to that structure by insisting that those who actually the produce legal documents have been professionally legally advised about those legal documents, and that the fitness of the circumstances have also been professionally considered (and, possibly, to get a lawyer’s certificate confirming they have done both things).
Mounteney Solicitor’s legal advice certification service is outlined here: https://www.mounteney.com/finance-services/certificate-of-independent-legal-advice/
Regulated lawyers are required by their professional bodies not to act when there is any issue of possible ‘conflict of interest’ – so lawyers advising clients will usually have to act independently of any other lawyers who might be involved for any other actors in the arrangement. Within Mounteney Legal Group, a Mounteney Complete-type arrangement might be possible: https://www.mounteney.com/residential-property/conveyancing/fast-conveyancing/
Giving legal advice is different to (and goes well beyond) merely witnessing a signature on a document – see https://www.mounteney.com/finance-services/witnessing-documents/ for details of what is involved in witnessing a signature. Solicitors are often asked to witness signatures because professionals are taken to understand precisely what is entailed in such a witnessing (which lay-witnesses do not always appreciate).
