Warren Gatland insists he has picked a British and Irish Lions squad with the firepower to take on South Africa, but Kyle Sinckler misses out as the highest profile casualty.

Exiled England number eight Sam Simmonds has defied the indifference of Eddie Jones to win a place in the 37-man group, leading a list of bolters also including Bundee Aki, Chris Harris and Jonny Hill.

But Gatland has displayed his ruthless streak by overlooking Lions stalwarts Johnny Sexton and Jonathan Davies, while the likes of Billy Vunipola, Henry Slade and James Ryan are also big-name absentees.

It is Sinckler's omission that has caused the greatest stir, however, with the 2017 Test Lion and cornerstone of the England pack losing out to Ireland's Tadhg Furlong and Andrew Porter and Zander Fagerson of Scotland.

"That was a tough call. Tadhg Furlong had an outstanding Six Nations and Zander Fagerson has really come on from a Scottish perspective," Gatland said.

"From a penalty perspective, Scotland probably came out on top of all the teams during the Six Nations at scrum time and they scrummaged pretty well.

"Then Andrew Porter gives us that flexibility to be able to cover both sides. Kyle is unlucky, but there are other guys who we feel can do a really good job for us."

Sinckler, who only became an England starter upon his return from New Zealand four years ago, used social media to voice his disappointment at being left out.

"Honestly gutted not to be involved. Appreciate the messages of support," the powerful Bristol front row said on Instagram.

"Not a time to feel sorry for myself and blame others. Let's get behind the squad, wishing the boys all the best. Looking forward to watching the boys carve up. Go well."

Gatland described the task of picking the squad as the toughest of his long career, but always kept in mind the need to have players with the physicality to face down the world champion Springboks.

"If you were going to Australia or New Zealand then the make-up of the squad and certain players may look a little bit different," he said.

"We have tried to get that balance right knowing we are going to have to roll our sleeves up on a few occasions and go toe to toe with the South Africans.

"South Africa have gone back to their DNA. Their mentality is about being physical and winning that physical battle. It's going to be brutal at times.

"We want to play some really good rugby but at times we're going to have to get in the trenches and battle it out with them because it's going to be tough.

"We feel like we have picked players who, if we are in that situation, can do that sort of job for us."

Setting the tone will be captain Alun Wyn Jones, who embarks on his fourth Lions tour as one of five locks including the unexpected presence of Jonny Hill and Courtney Lawes.

Gatland has increased his intended squad size by one, adding an extra back-five forward in anticipation of the physical onslaught awaiting across eight fixtures in South Africa.

Three number eights in Simmonds, Taulupe Faletau and Jack Conan travel with the imposing Tadhg Beirne earmarked as a blindside flanker, although he also offers second row cover.

And while there is no place for the injured Manu Tuilagi in midfield, Aki and Robbie Henshaw are ball-carrying threats in the centres.

"They give a good balance. Bundee plays the same role as someone like Manu could do. Brings that go forward, that physicality and has a fantastic mix in his game," Gatland said.

"South Africa are going to have a big physical midfield and be really direct. We have to have centres to mirror that if we need to, but we also have to go and play some rugby."

Gatland said that a revised version of the original tour schedule, which has been made necessary by the coronavirus pandemic, will be finalised soon.