Has this or something similar happened to anyone else?

Over the last few weeks I have not received a couple of expected letters from Royal Mail. I've worked around it, but last week I telephoned the company I was expecting the letters from. The letters relate to a financial investment and so contain personal financial information. They told me they had been sent and to report it to Royal Mail, because they had actually sent 4. This I did. Then I started to work out that I have received very few letters over the last few weeks - in fact I can only recall 2. I also remembered that a neighbour with the same postcode and surname as me, moved recently.

I telephoned Royal Mail again and mentioned this and have now been informed that the person had set up a mail redirect 6 weeks ago and not only has the same surname as me, but the same initial.

It seems highly likely that my mail has been mistakenly redirected to this person for weeks. This mail not only contains financial information amongst other bits and pieces, but also very probably medical information.

The case is still ongoing in Royal Mail and it is not yet proven that my mail has been mistakenly redirected, but it seems very likely given that I've had very little mail since they moved. I should find out next week.

What I'd like to know is what course of action, if any, can I take for careless loss of my personal and highly confidential data