‘herd immunity’ – involving the disease to move through the population, without interventions, in the absence of a vaccine – was the Government’s policy and that this “could have been an area where there was political pressure” influencing expert advisors" https://bylinetimes.com/2020/04/13/did-experts-fail-to-speak-truth-to-power-over-targeted-herd-immunity/

This is exactly my understanding of what happened here. That this was not the scientific advisers who told the government to create "herd immunity", but the government who told their advisers this was their aim, and the advisers gave advice in that context.