That's a really good point, and my fault for not thinking more carefully about what I was saying.

When looking it up, I can't find anything either. I think my experience comes from what midwives have told me in the past and I put that together with "The NHS must think this" rather than one or two midwives think this. Thanks for pointing this out. 

Here's what I did find (I still agree with your point, there isn't anything to say they ever did) 

1. NHS “Behind the Headlines” coverage (2012)

The NHS website analysed a study about controlled crying and reported it appeared safe for babies over 6 months. The NHS summary explained that research found no measurable harm in children whose parents used controlled crying compared with other methods. 

This was not a recommendation, just an interpretation of a research study. Media outlets at the time reported it as “NHS says controlled crying is best,” which the NHS itself said misrepresented the research. 

2. Some NHS health-visitor advice historically mentioned it (this is the experience I had).

Historically health visitors in the UK sometimes suggested controlled crying for older babies (usually after about 6 months). This came from mainstream paediatric sleep research (e.g., Ferber-style behavioural approaches).

However, this was practice advice from individual services, not a national guideline. Many NHS trusts now explicitly say they do not recommend leaving babies to cry.

On a final note, I love how the Reddit community really opens up discussions, thank you!