Rapha, nice but a bit pricey?

Alternatively, wash your armpits using soap and water

Sigh... I guess that's aimed at me. Yes I do wash my armpits with soap and water. Quite partial to this at the moment

Have you washed it in-between those 5 commutes?

Yes I have, but not with Rapha wash. I wonder if that's where I'm going wrong ?

you can also try riding slower to prevent the build up of sweat

Unfortunately my commute is down one side of a valley, and then up the other side. I could try walking I guess to reduce the chance of perspiration. Will try that.

Additionally antiperspirants are known to reduce the odour of sweat

While I'm open to most things, I take it you haven't experienced the smell of 100% polyester and antiperspirants ?

Try commuting with some kitchen roll stuffed in to your pits, buffer zone.

Thanks, I'll also try that on my way home while walking up the other side of the valley just to be sure

or, just wear it as casual clothing. for drinking coffee in, natch.

I have other nice but a bit pricey garments for doing that very thing.