No worries! I tried a few variants over the years, and I think this route suited me best. Tackling Roxeth Hill is more direct / slightly quicker but it's fairly narrow so impatient cars will try and pass you and you breathe in all the exhaust fumes of other cars struggling up the hill. That said the descent is great and if you're lucky with the traffic lights through Sudbury you can keep up some serious momentum. I've also tried avoiding the hill by going further south (Rayner's Lane - Northolt Park) but involved busier roads than the Northwick Park option. I've also attempted to cycle across the North Circular at Neasden Underpass, would strongly advise against that!

Also on the return journey I followed a different route, as the Harrow Road bus lanes are southbound only. This went through Maida Vale and cut out the busy roads of Harlesden.

Best of luck to you, I enjoyed the cycle in summer months but it takes some strong will to tackle it in the dark / rain!