Dunwich Dynamo 2018

Depends which train is running that day, service starts in Norwich and runs via Ipswich. Most of the time it's a very large, slightly newer train where the drivers cab doubles as bike storage - in which case there's loads of room. Sometimes on some of the more off-peak trains it's a proper old knackered looking thing that has next to no bike storage at all. Unfortunaterly I don't know if there's a way to find out which trains run and when, could be worth ringing them.

If phone greater anglia customer service directly they can book you a bike space and give you a separate reference number and you get a ticket you can stick on your bike so it's all legit - assuming there's any spaces left.

Sadly Greater Anglia have historically been cataclysmically unhelpful and basically choose to not recognise the existence of the dynamo and I've heard of them simply turning away any and all cyclist who turn up without a proper reservation, even if there was space on the train.