tax enquiry advice needed

A new client (taxi driver) has lost all his not very well kept records for the last few years. His explanation was a difficult relationship breakdown and family issues with moving from one place to the next.

The tax returns for the last 6 years have not been prepared nor submitted by the ex-accountants. He now has received a letter from HMRC requesting Income & expenditure schedules for the past 6 years.
I am stuck as the client has no records at all apart from a letter from the taxi office confirming the base rent. No figures for fuel, mileage, repairs, insurance, or sales.

He has however provided a single set of accounts from a few years ago but without any supporting data. I am not sure of what i can possibly. I can't even get intouch with licensing authority as he has changed a number of vehicles over the period and does'nt have any records!
Is it advisable to send through the single set of accounts of a few years ago prepared by the other accountant and prepare draft I&E for the remainder years with exactly the same figs and explain to the inspector that there is no other option and he should consider that as the best estimate?

Apologies for the rambling, i've never seen a case as bad as this one. Thanks for your comments.