By the way, I finished Some Do Not a few days ago and am looking forward to starting our second installment. I just needed a few days of a breather.
For a while I was finding Macmaster insufferably dull, but now that I'm through the first book, I'm finding him to be an intriguing foil to Tietjens.
First, Tietjens' main problem is that he has absolutely no social skills, and Macmaster is clearly a gross social climber. Tietjens can, based on his family name, afford to tell important people off, whereas Macmaster does not have this luxury. If Macmaster wants the prestige and the knighthood and the money, he has to struggle and kiss the right asses, whereas Tietjens can pretend not to care about his job or the impression he creates or the vicious rumors that are spread about him due to his (as the college kids like to say) privilege. The reason anyone is spreading rumors about Tietjens at all, I suspect, is primarily because he acts as though he's above it all, and there's nothing venial people hate more than feeling as though someone is acting cold and superior.
Macmaster has every right to be ambitious and create his salon and marry the woman he loves, but he often does this at Tietjens' expense, literally and socially. The household he has created is run on Tietjens' dime; Tietjens takes the fall for scandalous insinuations about Edith Ethel; and by the end of the first book, Macmaster takes credit for Tietjens' statistical work and claims a knighthood. Macmaster certainly isn't rushing off to the trenches on behalf of his country and is instead manipulating numbers that will result in the deaths of more men (yet Tietjens is also giving him the ammunition). In addition, although Macmaster does care about Valentine and Tietjens, he's letting his wife and his social ambitions interfere with his relationship with his best friend.
Edith Ethel views Tietjens suspiciously--as though he's keeping his friend purposely indebted to him for malicious reasons. Tietjens, I'm sure, sees his sacrifices for his friend as altruistic, but he doesn't see that putting himself in the position of philanthropist is not the same as being a friend. If you do huge favors for someone while at the same time acting as though it is no sacrifice, it implies that you are superior to the person on whose behalf you are acting, that you have so much by position and wealth that the sacrifice means nothing to you. Macmaster, I'm sure, is very aware of his financial and intellectual dependence on Tietjens and resents him for it on certain levels.
As their social positions are reversed, I'm interested to see what effect Macmaster has on Tietjens' life in future installments.