Can you travel from Northern Ireland to Britain without a passport or driver's license? In theory there are no border checks but ferries seem to demand photo ID.
There is no border between NI and England, therefore there are (in theory) no border checks.
As a UK citizen in the UK, there is no obligation to carry any form of ID.
However, in practice there may be officers checking people and asking for ID as they disembark. If you had none, then they could reasonably detain you for a short time while verifying your identity in some other way. Therefore it is advised to carry some form of ID (I used a railcard, but a bank card should suffice).
Non-UK and non-Irish nationals require a passport, according to this web page at Irish Ferries.
Stena Line, which sails from Northern Ireland to Great Britain, is somewhat more vague about requirements (see links above).
Identification is required even on Northern Ireland to Great Britain ferries, such as:
- driver's license
- European identity card
- bank cards
- photo ID (school or college)
- utility bills
- birth certificate
So, strictly speaking, it appears as though photo ID is not required, but some sort of verification of your identity is.