Finding Absent Landlord For Leasehold House

I'm hoping someone can point me in the right direction.  My mother and father bought a leasehold house in Manchester in 1970 and my mother is now updated from 2011 as having the good leasehold and being sole proprietor in part B. However she has not been charged any ground rent for a long time and no longer has the address where she sent the £8 cheque to annually.

The title on the land registry mentions in part A, the creators of the lease in 1955 with J Maunders & sons named and the original purchaser. Maunders became a plc in the 1960s, were bought out in the 1990s and the company that bought them was taken over by Persimmon  20 years ago. 

The title says the landlord's title is registered on line three of part A  but does not say who it is.

I want to try and clear this up before my mother needs to sell or passes on. I know I can try and go to court but was wondering if the Land Registry would have the landlords details without showing them?

Sorry for the longwinded question.

Matthew - if the freehold is registered then the details should be revealed when you search online against the property address - Search for land and property information - GOV.UK
If it doesn't then what's the leasehold title number please?

Thanks Adam. 
The title is LA245313. We have a letter from 1970 where Authority Securities Ltd were believed to have the freehold but they no longer exist.

I hadn't realised there would be two titles for the same property. I only had the leasehold title and using the link above found there is also a separate freehold title which I've now downloaded and got a name to work with.
Thanks again.