An interesting historical debate on the growth of LTN and the decline of SEN. All the contributions have validity and there are some other factors to add to the picture.
In the early days of the growth of the inclusive tour market much of the business was road/air/road using short cross-channel routes like SEN-OST. It was even claimed that SEN-OST was the busiest international air route in the world ! This model fell into decline after some high profile coach accidents on European motorways and the natural progression towards more direct flights. Channel Airways, which had been a major operator on these routes, moved with the market by buying Viscounts which could operate direct to the Med resorts. Channel had contracts with several major tour operators. Its biggest customer was Clarksons.
The current terminal at SEN dating from the mid 1990s is only approximately a quarter of the size of the building in use in the 1960s
As the tour market matured the tour operators began to favour LTN for its access not just to London and the south east but also to the Midlands. Add to this the inability of the jets to fly nonstop to the Med off SEN’s runway and SEN’s demise in the holiday market was sealed..
In fact I suspect in overall terms it was LGW rather than LTN that took more traffic from SEN. Two companies (Overseas and Air Safaris) moved out to LGW though they did not last long. Some Scandinavian companies moved their
operations too.
Agreed with the comments about Southend Council. I think they were completely out of their depth, they had no idea how to proceed. They were terrified by the noise lobby and they considered it politically unthinkable to propose developing their airport still further. In this respect at least they were probably correct.