Why should they cannibalize the LCY service? In fact, any seasonal summer service to London that is axed could potentially shift passengers to the LCY service. As that service probably sees less demand during the summer than at other times of the year, it appears to be more sensible to make some cheaper tickets available on those flights than run a dedicated LTN service that leaves both services with half empty planes. It is not as if JER passengers could go for a LHR service instead of LTN anymore....