Just checking: RCT = Randomised Controlled Trials?
Yes - which are seen as the gold standard for new drug and other medical intervention research (such as a new surgery technique). The problem is that the few small scale RCTs on mask use have been looking at the impact on the wearer and not people the wearer comes into contact with. So in a situation where your mask protects me, and my mask protects you, there is zero RCT evidence. But more importantly, there's a lot of lab science which looks at how viruses are transmitted in the air through water droplets from the nose and mouth, but all of this is being ignored by SAGE and the government. Also, the WHO is being really naughty - it recommends that the public wear face masks in time of pandemic flu but not for COVID. If anything, given the increased infectiousness of Covid compared with flu, their recommendations should be the other way round.
There is a big debate about the limitations of RCTs in informing public policy - what works in a controlled clinical trial might not work in a public setting for a whole load of reasons.
The irony for me is that the government recommends that we sneeze into a hanky (or our elbow if we don't have a hanky) - try searching for an RCT on the efficacy of sneezing into your elbow. I don't think you'll find one - it's just plain common sense.