Upgrading from possessory to absolute title

I am purchasing a property where some of the garden has a possessory title. The current owners were granted the possessory title recently but the land in question is clearly included on the photos and plans from when they purchased the property ten years ago. My question is, does the 12 year ‘clock’ for upgrading to a title absolute start from 10 years ago (when the current owners purchased the property) or from when we become the owners of the land?
thank you for any information 

Mrs P - the timescale re the 'upgrade' starts from the date of actual registration of the possessory title. So 12 years from the date of registration.

Thank you. Another question- when the possessory title is granted, do the owners of neighbouring land receive notification that the request for a title has been made? 

Mrs P - before possessory title is granted we will usually notify adjoining landowners to see if they object/consent to the registration. 
Once those checks have completed we don;t then notify them once the registration has been completed for example