If you hold an Oyster travelcard, valid for zones 1 and 2, with additional PAYG credit, and a paper Boundary Zone 2 - Watford Junction ticket (groupsave, in case you are wondering why you wouldn't use the PAYG credit), would you be able to get through the barriers at Euston using the BZ2 ticket?
If not, would you be charged a maximum fare if you touched in at EUS using Oyster and didn't touch out at WFJ?
If not, would you be charged a maximum fare if you touched in at EUS using Oyster and didn't touch out at WFJ?