From Aviation Herald:
A Ryanair Boeing 737-800, registration EI-ENI performing flight FR-9128 from Liverpool,EN (UK) to Oslo Rygge (Norway), was enroute at FL390 over the North Sea about 160nm northeast of Newcastle,EN (UK) when the captain became ill and was unable to continue duties. The first officer declared emergency and diverted to Newcastle descending the aircraft normally. The aircraft landed safely in Newcaste about 40 minutes later.
Passengers reported the crew announced the captain was ill.
EI-ENI switched with the scheduled DUB flight at NCL (EI-DLT) and returned to DUB with 'DLT going on to RYG.