Yeah you’re looking strong at the mo @leahnp!
I did something similar. Eldest was at gymnastics, my first drop off so I planned a little getaway to use the hour. Happy to see I could get into the lanes pretty much immediately. Coincidentally I was just round the corner from a big hill I rode for the first time last sunday, so thought I’d give that a bash as it was 4.5km to the top, so perfect distance run.
I’d spotted a segment for the hill and knew it was 8mins or so for the kom, so planned to have a crack. Started the run and immediately felt sluggish, so decided I couldn’t be arsed to go for the kom. But I’d use it as a recce for next time.
Legs were feeling shite on the hill. Kept having to stop to walk, when I really shouldn’t have (though it does get bloody steep, over 20%). Was only running with hr on the watch so was just busy berating myself for being so weak.
I’d figured my time would be 10 mins plus, so I’d completely given up on this and any future attempts.
Get to the top, hit lap and it was 8 something. Bloody less than 11 secs off the kom! 
Had I had the screen on the watch instead of being a flippin wuss, I could’ve easily mustered up a bit of mtfu and got going and taken the kom out (I finished 2nd by less than 11 secs).
Turns out I missed out on the kom for the descent (which I didn’t know about) by a matter of secs as well! Oh well, next time. 
Ended up running a bit progressive on the kms back to the car finishing in solid tempo+ territory.
Sorry bit of a long, Shakespearean soliloquy there! Cos it’s only gonna be me listening!

Anyway.
10km in 42.30 with 235m elevation.