Maro Itoje and Alun Wyn Jones will shift from friends and former room-mates to rivals when England host Wales Saturday.
Emphatic wins by both teams in the opening round has elevated the excitement surrounding the Six Nations showdown at Twickenham and the clash between Itoje and Jones will among the duels taking centre stage.
The pair grew close on the British & Irish Lions tour to New Zealand after rooming together for two weeks and their bond has led to a public exchange of ribbing centred on cocoa butter and baldness.
"We got on very well during the Lions tour, although his musical tastes are very different to mine," Saracens second row Itoje said.
"He let his hair down. I'm fortunate enough to have quite long, free-flowing hair. He's severely balding, but I think he's come to terms with that now."
In response to Jones' complaint over his refusal to share his cocoa butter, Itoje replied: "First of all he didn't ask and secondly he doesn't use it. He'll be all right."
Itoje and Jones are at contrasting stages off their international careers, the Englishman's 18 caps comparing unfavourably with the 123 held by his rival from Wales.
"Alun's very professional, trains hard and is diligent with his preparation," Itoje said.
"Obviously going on tour you spend time with the other home nations and you pick up things. The Welsh players are like this, the Irish players are like that etc etc.
"Alun works very hard. He's a nice guy as well. I got on very well with him on tour. It was a good experience. I know him better because I played with him and I've played against him twice already this season when Saracens played the Ospreys.
"But that isn't even in the slightest bit difficult for me. It's a completely different setting, different team, different environment."
The Lions tour also offered Itoje the chance to work under Warren Gatland, the long-serving Wales coach who is plotting England's downfall this weekend.
"Warren is very experienced and he's a good coach," Itoje said. "He gives his teams confidence and I'm sure he will give his Welsh team a lot of confidence this week -- especially after their game against Scotland.
"The rivalry with Wales is big. This was my first start a couple of years back, so the whole magnitude of that occasion was massive.
"There will be a lot of passion. It will be intense. It will be physical. It is a great game to be a part of and I'm sure Twickenham will be rocking."