This is a photographic technique post. So, if you don't want to see what it's all about, look away now.
I had acquired some cheap, expired and seemingly badly kept HP5 from someone in Spain. It was cheap - did I mention that? When shot at 800 asa ish it seems to work ok ish. Wasn't sure about the developer to use though. Tried Rodinal but it wasn't brill. Tried LC29 and that was a little better but now I have tried some Promicrol acquired from some-place down in England, cheaply.
The only down-side was that I stared the development without checking the times and dilutions. 1:30 came to mind so I used it. Unfortunately, there is no data for this dilution so I turned to my usual technique in these circumstances - I winged it!
Yep, this is 18 mins @ 22C [ish] 1:30 dilution. And it seems to work too.