Beyond Itoje, none of them are set in stone imo - Martin more than Chessum, but he is by no means nailed on to play 6 imo.
Itoje will be set in stone, but should he be?
Traditionally thought of as our best scrummaging lock, but now hard to think that Martin doesn't provide more power.
I'd say Chessum is just as good in the line out if not slightly better. Bit taller too which is always helpful.
Martin's probably better carrying in the tight, similarly Chessum in the wider channels.
In the tackle Martin probably hits hardest.
Itoje's best at winning turnovers, but offset by the number of pens conceded.
Over 80 mins Itoje (on a good day) probably has the highest overall work rate.
In terms of impact Itoje's been a constant but can sometimes go quiet in terms of his own performance and impact on others. The team simply seems to look better with Martin in it, it may be that his simple agggression inspires people more than Itoje's more cerebral approach.
Itoje has the experience and is probably the best all rounder. But he's a hybrid. Would you take him over Martin as a TH lock? Or over Chessum as the athlete and line out specialist? What's the best combination?
I think there's a place in the team for both Martin and Chessum. They complement each other well, are a club combo and I'd love to see them given a shot in the row. Won't happen, obvs.
At 6 carry on investing in CCS. Power with and without the ball and an improving line out option. Work to do on skills, but don't wait until he's the 'finished article', he can already contribute a lot.
Underhill at 7. Nuff said.
Earl at 8 for now. Summer I suspect was more tiredness than anything else, but in time I want to see a bigger guy there whether T Willis or CCS.