Looking for a running rucksack to commute to work and carry shirt, trousers (shoes will stay there) and lunch.
Been looking at OMM Ultra 15 and Ultimate Direction Fastpack 15.
Fastpack is a fair bit more expensive but has flask mount on shoulder and what looks like good access to stop clothes getting creased.
Anyone use these (or others) and can offer thoughts.
Also plan to use it for some ultra training over winter in between TR workouts (makes the hydration more useful).
Hi I use Overboard back pack for run commute, I carry waterproofs, warm coat, shirt, trousers. I have used for the lest twelve months and it is still good as new. The back pack is also waterproof.
I really liked the OMM Ultra 15, running up to half marathon distance.
Find a way to roll up your clothes to avoid creasing, and wrap in plastic bag in case of rain/splashes from cars.
Run commute is fun, but ultimately leaving clothes & washkit at work is the way forward. 
I highly recommend a Salomon Advanced Skin 12 (I think I have an older version with a different name tho). More of a west than a backpack, but the materials are so stretchy that you can fit quite a lot. And it’s not too big and bothersome to use for a long adventure run on the weekend. I just make sure to pack everything in zip lock bags to keep things dry. It’s been going strong for 4 years now.
Thanks for the suggestions.
@JoeX you’re right. My plan is to leave as much at work as I can, or take it in by car at the beginning of the week when I need to.
Used to run commute as well. This was before these vest like backpacks were available. Definitely get a vest style one, you hardly notice them. I also brought things once a week by car or bike. Running twice every day wasn’t sustainable for me anyway
I used to use a small ~15l Deuter with a frame and mesh straps. Put a webbing belt went around the middle and cinched it tight to stop anything bouncing around, nothing worse than jiggling stuff in a pack.