Ok, after around 50 minutes of going through and skim/ reading some of the reports a few things are noticeable:
a) The final report is dated 2014 so we could potentially assume that this was just an idea that took up lots of money to research into... (Also not sure why the BBC is reporting on a 3 year old matter)
b) They specifically state that "optimised aircraft" will be utilised with the landing gear heights increased, thus rendering most current aircraft useless...
c) In regards to take-off, they state its is possible after simulating a 747-100 (they couldn't find necessary data for current gen aircraft) takeoff at MTOW in a program (Flightgear) However, during landing the max lateral speed increases momentarily over 1.2ms^2 (what they deemed dangerous) (I also found the wording very unprofessional here... they say "for a few moments" instead of quoting exactly how long it goes over that limit that they determined)
But in summary, if you do glance over the report, it is evident that overall it is quite biased towards the circular runway idea (no surprises), there is a lack of data clearly presented (indicative of them trying to hide something perhaps? and yes they do give data but it isn't clearly visible in summary) and they do take some simplifications here and there (They use Wikipedia for crying out loud... no professional does that, at least someone could have had the decency to quote what the wiki quotes...)
Now all of this does not mean that I condone the people behind the research, they just had an idea or were asked to further the idea, that's their job. But, just because you're a professional does not mean that you know everything, sometimes you miss out the most obvious