Stobart could operate SEN, but is there any appetite for this at either EI or BE. IE have good coverage of London at LGW and LHR, in addition they have a codeshare on BA to LCY. What would SEN really add to their network at this stage?
If it is at Stobarts own risk, neither airline would likely give a fiddlers, but EI might be concerned about diluting revenue out of London.