XR is fond of citing political scientist Erica Chenoweth’s ‘3.5 percent rule’ (see eg. 'XR: The Plan') – an empirical observation that it ‘only’ takes ‘3.5% of a population engaged in sustained nonviolent resistance to topple dictatorships’ , based on the analysis of a dataset of over 100 major nonviolent campaigns that took place between 1900 and 2006. 
It should be noted that:
(A) the dataset only considered ‘antiregime, antioccupation, and secession campaigns’ ;
(B) very few of the antiregime campaigns in the dataset targeted democratic regimes ;
(C) none of the antiregime campaigns attempted to unseat a western industrial democracy. 
Does this mean that the ‘3.5 percent rule’ will not apply in the UK? Of course not.
I’ve no doubt that if two million people in the UK were to engage in something like mass non-co-operation in a sustained way for nine to 18 months then they could accomplish incredible things. 
However, I strongly doubt that XR’s block-roads – mobilise-to-block-more-roads – block-roads-again cycle is capable of getting us there.
Fortunately there is a much richer history of nonviolent methods and campaigning that we can draw on as we try to build towards such a goal – a history that can be explored through more than 1,190 examples of nonviolent campaigns detailed in Swarthmore College’s online Global Nonviolent Action Database: www.nvdatabase.swarthmore.edu
 Erica Chenoweth, ‘It may only take 3.5% of the population to topple a dictator – with civil resistance’, Guardian, 1 February 2017, https://www.theguardian.com/commentisfree/2017/feb/01/worried-american-democracy-study-activist-techniques. Elsewhere, Chenoweth has glossed this this observation as ‘no government could survive if [3.5%] of its population mobilized against it’: https://rationalinsurgent.com/2013/11/04/my-talk-at-tedxboulder-civil-resistance-and-the-3-5-rule/.
 See Erica Chenoweth & Maria Stephan, Why civil resistance works: The strategic logic of nonviolent conflict, Columbia University Press, 2011.
 Ibid, p.13.
 See ibid, pp. 233 – 236 and its online accompanying methodological appendix, which contains brief narratives of all the campaigns: https://www.ericachenoweth.com/wp-content/uploads/2012/01/WCRWAppendix-1.pdf.
 In a 2019 article, Chenoweth commented on her ‘3.5% rule’: ‘That sounds like a really small number, but in absolute terms it’s really an impressive number of people. In the U.S., it would be around 11.5 million people today. Could you imagine if 11.5 million people — that’s about three times the size of the 2017 Women’s March — were doing something like mass noncooperation in a sustained way for nine to 18 months? Things would be totally different in this country.’ https://news.harvard.edu/gazette/story/2019/02/why-nonviolent-resistance-beats-violent-force-in-effecting-social-political-change/