Immediately, the lever feel was a lot firmer, unlike before I was able to lift up the back wheel from heavy braking quite easily - I was able to finally do stoppies unlike before. I figured previously when I had used conventional coiled brake cable housing, even with the brake lever touching the bar I could never lift up the back wheel, it was due to the housing compressing. Increased braking power was definitely a good thing in London traffic. However on the first evening on my bike returning from work I noticed that the steering feel a little strangely light, I looked down and was aghast that the fork was bent! As you can see from the photos, it's quite apparent that the force put through the reaction arm overcame the elasticity of the fork and bent it back right where it attaches.
The paint is cracked around the area where the reaction arm attaches, the fork is also twisted from the uneven load put on the legs, all this from a few stoppies! Please keep in mind that I weigh under 70kg as well so there was no real extreme conditions that caused this to happen. I figure though that the fork was designed for rod/caliper brakes originally which would have focused all the braking force in the crown not midway up the left fork leg so this isn't a complete surprise.
As I have no intention of going back to caliper or rod brakes, I think my only real long term option is to replace the fork with one that is more suitable. It's a real shame as these are the original forks, I even have the key that fits in the fork lock too! To this end I've ordered a fork with a proper drum brake reaction arm which should be strong enough to handle the force from the drum brake. As this is a daily driver bike which gets ridden everywhere, reliability and my safety are paramount so I think this is the right choice. Stay tuned for more!