Hugo Keenan, Garry Ringrose, Iain Henderson and Oli Jager all took part in Ireland training today and remain in contention to face England.
Full-back Keenan injured his knee in the round two win over Italy and missed the victory over Wales, while centre Ringrose has yet to feature in the Guinness Six Nations championship as he recovers from a shoulder injury picked up while playing for Leinster in January.
Second row Henderson came on as a replacement against Italy but suffered a foot injury for Ulster in the URC two weeks ago.
Prop Jager won his first cap in the victory over Wales in round three and has a knee injury.
Fellow tighthead prop Finlay Bealham had initially been released to Connacht last week but was recalled into Ireland camp.
"We were all on the field today, it was great," scrum coach John Fogarty told reporters as Ireland prepare for Saturday's round-four meeting in London.
"Garry and Hugo, Hendy, all trained today, Oli as well.
"So, yeah, it's such an important day for us to be on the field. A healthy squad training today is important for selection and it was great they were all on the field."
Asked about Keenan, Fogarty said: "Well, he trained today.
"Again, they are on the road to recovery, training on the field today live was important for them. We’ll see how they got through the session.
"We’ve another session tomorrow, which is the most physical session of the week where we’ll properly test our plan and the players so we’ll see how he gets through tomorrow and then Andy [Farrell, head coach] will select his side.
"[Today] it’s full speed, there’s no huge contact in it, it’s kind of a coaching day.
"Monday is forming a plan, Tuesday we put it on the field and we’ll see the timings of our launch plays and how our defence works and tomorrow we’ll test that full contact, we want to get as live as possible, ready for what's going to be a huge test in Twickenham."
Ireland have won their last four games against England, and two of their last three championship games in Twickenham.
They wrapped up the Grand Slam at home to the Red Rose last season and can win the Six Nations with a five-point haul against Steven Borthwick's men, who have beaten Italy and Wales and lost to Scotland.
"It's Ireland-England, isn’t it. It’s such a brilliant place to go and play rugby," said former Leinster hooker Fogarty when asked about the rivalry between the sides.
"The English squad rise to play in Twickenham. I know that they will be hurt from the last game but they will be so proud to play in front of their home support.
"It’s a cauldron, the stadium itself generates a huge amount of noise, which can be chaotic in the mind of players.
"It’s a huge rivalry but where we are right now is preparing for that cauldron, preparing for that energy that is Twickenham.
"That’s what’s to the front of the players’ minds, trying to make sure we are the best version of ourselves, representing Ireland in a calm way where we can see what’s in front of us and play our game.
"Rivalry is important but where we are at now is preparing to perform is what’s going through the players’ minds.
"They are a week further down the line with their coaching group now, they'll be a week further understanding what it is they are really about.
"You can see the power game, you can see the energy within the group.
"I’m sure they will feel they haven’t represented themselves to the best of their abilities just yet. What an occasion to click and show it.
"It’s a good coaching group, they are clear in what they need to do and there’s a lot of power in their side. We are very conscious of the mentality we need to have to make sure we are able to perform with that pressure.
Watch England v Ireland in the Under-20 Six Nations on Friday from 7pm on RTÉ2 and RTÉ Player, follow a live blog on rte.ie/sport and the RTÉ News app
Watch England v Ireland in the Guinness Six Nations on Saturday from 4.45pm on RTÉ2 and RTÉ Player, follow a live blog on rte.ie/sport and the RTÉ News app and listen to live commentary on RTÉ Radio 1
Watch Wales v France in the Guinness Six Nations on Sunday from 2.30pm on RTÉ2 and RTÉ Player
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