I ride a hub geared pompetemine with full mudguards and rack. Slime tubes in some kind of toughened tyres. Two pannier bags:
Bag 1: laptop, charger, mouse all in neoprene sleeve. Work notebook and whatever paperwork I’m having to carry around. Pre ironed shirt folded round towel (I take a small one in every day, they stink the office out otherwise) with underwear and tie – all in waterproof bag.
Bag 2: lunchbox, some old waterproof trousers for inter office rides during the day, small toolkit with 2 tubes, multi tool, levers, patches, spanner. Pump. Very small lock. Everything else like bb, pass, wallet, phone, etc.
Moving to panniers after years of carrying heavy laptop on back has been a revelation.
I leave a couple of suits, pairs of shoes and wash kit at work. And have just ordered a brompton to leave in the office for journeys during the day.
Agree that preparation is everything. I lay everything out the night before…like many above I have forgotten things (cuff links the main offender)
Kit wise, old padded shorts, humvees (3/4 all year), whatever Jersey I put my hands on, showerproof coat. As above, spend money on really good winter gloves if you feel the cold…have a couple of buffs ready for the cold months, and sealskin socks can be good unless you go through flooded roads.
I enjoy it more in the winter…love the feeling of being up against it.