SIGMA, the glider to incorporate all possible technical advances.

The link below produces Nick Goodhart's essay on the marvels of
Sigma, a Britsh effort to make a world beater; this was before it flew!
It failed probably due to excessive mechanical complexity and the high
pilot work load. also the complicated extending flap proved difficult
to implement and seal; the handling left a lot to be desired.
someone claimed Sigma was designed by committee!
It was abandoned with what were considered intractable problems,
and put up for bids; it was donated to Dr David Marsden, who had already
designed and flown the Gemini with slotted extending flap.
While on sabatical at Cranfield, (RAF research) he made conversion of Sigma a research project; when I visited him at Cranfield , he showed me
the massive Sigma wing with installation of his own slotted flap
in progress. This was a sucess.
It was test flown and the flap system worked as expected. However it was
found to have really challenging handling problems, especially on landing.
I expressed interest in flying it, but was refused as the only other
highly competent pilot to fly it found it a handful.

John Firth

PS Nick Goodhart chooses 100KM TRIANGLE as a hypothetical task;
these days, the challenge would be at least 500 KM and not much
talk of stopping to thermal!