Did your husband board at a station WITH a ticket office or a ticket machine if he did then he has committed an offence under British railways bye laws for failing to buy a ticket before boarding as it is a LEGAL requirement to buy before boarding If there are no ticket buying facilities the your husband will have a good chance to contest it where he may end up paying a penalty instead of the summons. I can not discuss this matter in great detail but get a copy of British railways buy laws and national condition of carriage