In fairness, all three of the scenarios modelled and produced in the Sage report of the 8th September were very wrong. Here's a link to the report.
https://assets.publishing.service.g...1017129/S1376_SPI-M-O_Consensus_Statement.pdf
Below is the conclusion aspect of the report that SAGE led with in their briefings to the media.
The two scenarios of R = 1.1 and R = 1.5 attempt to provide an envelope which contains the likely epidemic trajectory over the next couple of months. Even in the R =1.1 scenario, a large number of COVID-19 hospital admissions (up to around 2,000 a day) in England for a potentially protracted period of time is projected. Due to the uncertainties already discussed, it is not possible to project more accurately or further into the future. If combined with other winter pressures or seasonal effects; this could lead to a difficult few months for the health and care sector.
For completeness R = 1.5 predicted 7000 hospital admissions a day.
You don't need to be an expert in virology to see that the actual autumn wave, which was less than 1000 hospital admissions a day throughout the 8week prediction period of the report was significantly less than SAGES best case scenario.