The restriction on SEP was IMPOSED as planning restriction by the local council,
NOT the CAA, because of the risk to local residents in the event of an engine failure.
Being all knowing, they decided that if a twin engined aircraft had an engine failure on departure, it would be able to carry on regardless, with no risk to anyone.
These are the same idiots who decided that it would be perfectly safe to allow SEP to make instrument approaches, but they couldn't land at the airport.
Sadly the airport is now reduced to nothing, and once Finningly gets the go - ahead next March - which I'm reliably informed it will, Sheffield will close for good, with the site being developed as an expansion to the nearby "retail park", with the exiting and future businesses there, being subsidised by the South Yorkshire and UK taxpayers.