As part of the new Countryside Stewardship Scheme, an Expression of Interest (EoI) will be required if you would like to apply for the Higher Tier. This will allow Natural England to assess the priority of potential applications and allocate their resources accordingly. As they are scored at the beginning of the process, it will also give you an idea of whether to proceed to a full application or not. For those who are not deemed to be a priority, the Middle Tier will still be available, although this will also be a competitive process.
For further details and for a copy of the EoI form, see here.