Olivier Giroud is primed to join Chelsea from Arsenal for £17.5m on deadline day, a move that will allow the completion of a chain of transfers that takes Pierre-Emerick Aubameyang to the Emirates Stadium and Michy Batshuayi to Borussia Dortmund.

Agreement was reached in principle between the two London clubs after a day of exhaustive talks, with Arsenal anxious to conclude their own club record £55.5m move for Aubameyang. Even so, Giroud had still been included in Arsène Wenger’s 19-man match-day squad for Tuesday’s Premier League game at Swansea, which the France international began on the bench.

The 31-year-old’s priority has long been to enjoy greater playing opportunity before the World Cup, having started a solitary top-flight game this season following the £52.7m arrival of his compatriot Alexandre Lacazette from Lyon last summer.

Giroud will back himself to make a mark at his new club in what promises to be a fight for minutes with Álvaro Morata as Chelsea are in effect scrapping their established policy of not signing players in their 30s on long-term deals. Giroud is understood to have verbally agreed personal terms on the switch and is set to undergo a medical on Wednesday.

Arsenal, who have already taken Henrikh Mkhitaryan from Manchester United this month in exchange for Alexis Sánchez, had not been inclined to sell Giroud to a direct rival for a top-four Premier League finish. But their determination to set in train the deal for Aubameyang has forced them to compromise.

They have also had to take a hit on the fee, having originally wanted closer to £30m. Talks had appeared to hit an impasse on Monday evening but resumed on Tuesday in an attempt to smooth the wheels of the various deals. The £17.5m fee for Giroud is inclusive of add-ons.

Olivier Giroud gestures to the Arsenal fans after the defeat at Swansea - which may well be his final match for the Gunners. Photograph: Nick Potts/PA

Arsenal’s move for Aubameyang had gathered pace earlier in the day when Dortmund granted the forward permission to fly to England in order to undergo a medical and conclude the finer details of a club-record deal at London Colney. The transfer has been driven by Arsenal’s new head of recruitment, Sven Mislintat, who previously worked for Dortmund. He had been instrumental in taking Aubameyang to the Bundesliga from Saint-Étienne and, with the player having made clear he was keen on the move, discussions had progressed over the past fortnight.

Yet they could be concluded successfully only once Dortmund had secured their own replacement and, having initially considered Giroud, they opted to pursue Batshuayi.

Once Chelsea had opened talks over Giroud, Batshuayi was free to discuss the terms of a loan with Dortmund – the clubs had agreed a deal in principle – though he still trained with Antonio Conte’s squad on Tuesday and, with Morata currently injured, was expected to start Wednesday’s game against Bournemouth.

“He trained well and I prepared the game with him,” said Conte, who had spoken to Batshuayi before training to explain the situation. “It’s not the best situation to face but we have to. I have Morata injured and I don’t have other options. It’s not been easy to prepare.”

Chelsea on Tuesday night completed the signing of the Roma wing-back Emerson Palmieri for an initial £17m. Conte, who has made clear he has limited input into Chelsea’s transfer policy, had earlier suggested he had not personally recommended the player to the recruitment department.

“I don’t remember Palmieri [from his time in Italy] because he came to Italy only last season [it was actually 2015], when he had an important season for Rome,” Conte said. “Then he had a bad injury. He broke his ligaments. Now he’s recovering. I don’t know if he’s ready to play.”

The 23-year-old, who has been restricted to only two appearances for Roma this season because of that knee injury, has signed a four-and-a-half-year deal at Stamford Bridge and will provide cover at left-back for Marcos Alonso.

“English football is something I have been watching since I was 15 years old,” he said. “It is a really beautiful game over here but it is going to be even more beautiful to play it.”