Missing income???

I'm posting this for a fellow accountant who's embarrassed to ask

He has been asked to submit 3 years self assessment returns for a moderately well off 90 year old lady the information for which has been compiled by a family friend. It consists of all the usual income sources plus foreign dividends. By comparison with the 2007/8 return it is obvious that some income sources are mising /incomplete. The family friend cannot obtain/clarify any further and the taxpayer looks blank when questioned

The query put is what do you suggest the accountant does from the following?

1. Send an explanatory letter to HMRC (?trigger immediate investigation)

2. Allow the taxpayer to sign the form and submit it without further explanation (" It is HER return not his")

3. Resign and pay back the fees he has already been paid

4. Any other wise suggestions the multitude may offer

This is not something that should trigger MLR/SOCA procedures as it is completely innocent and not designed to hide income

Thanks for your help