How’s track and trace going? Some who’ll have to deliver it in England are pretty pessimistic. One public health director tells me: “I am worried… I’ve got a file of evidence for the pending inquiry.” More on @bbcr4today soon

Another person involved in discussions about scheme says: “Water needs to flow under bridge pretty quickly here to get an operating model that works… “do not underestimate the challenge”

And it’s not all about an app.

Concern is this – what happens once person declares they’ve got Covid? If teacher gets it, does school get automatically told, does council, GP? If that teacher’s son works in care home, who tells them? Who sorts tests in home? Whose job is that?

Who does all the stuff you can’t do from call centre? Who goes to see people who won’t download govt apps or take calls from govt-hired tracers? Govt plan says “local authority public health services” have role but those I’ve spoken to say no clear design for this yet

In jargon – I’m told both the system design and information flow just aren’t clear.

Another involved in this asks: “Where is capacity going to come from to do this? It won’t be short term. Will be mini outbreaks all over place for 12, 18 months.” Suggests fully operable system won’t happen before June.

Part of this is human. Folk outside PHE & NHS England feel shut out and patronised. PHE is unpopular. Really unpopular. Clear plan from new track/trace boss Dido Harding, good comms, quick change prob doable.

And on upside for govt, they are v positive privately and publicly about getting their 18k contact tracers hired by end of next week. Job ads show plenty will be handling calls from home.

But this won't all be sorted with an app and telephone calls. Govt knows that. But sorting the on-the-ground stuff is a real challenge