I Carry:
Waterproof trousers
Hi-Vis Jacket
Laptop (essential for work) Wallet, phone, keys etc
At Work :
Spare Innertube, and repair kit
Various tools I would need for tweaking or repairing a p******e
A spare handlebar (I dont know why i've kept it)
Oil
Optional :
Lights if I'm going to be arriving or leaving when its dark (or near dark) or if I think the weather may cause poor visibility.
Pretty much anything else I would need is at home.
This works well for me, as work and home are only 4 miles apart. I can live with an occasional failure because Its not too far to walk. Although, try to make sure that doesnt happen