We have developed a Mallory photocyclisation methodology in flow for the preparation of heterohelicenes including previously unreported thiahelicenes, azahelicenes and oxahelicenes. Aryl halides are tolerated and can be used to elongate the helicenes to longer, non-symmetrical structures through a 3-step Mallorycross coupling-Mallory sequence. While traditional Mallory reactions in batch can be difficult to scale up, our continuous flow methodology enables facile multi-gram syntheses with through-puts of up to 195 mg/h.