Arsenal have completed their first signing of the summer transfer window with Kepa Arrizabalaga joining in a cut price £5m deal from Chelsea . And his fellow Spain international Martin Zubimendi is expected to join imminently after a deal was agreed with Real Sociedad. A move for Brentford midfielder Christian Norgaard is also close to completion with the Bees admitting they are “happy” to see a key player of the Thomas Frank era move on. But Arsenal’s quest to find a new centre forward to take them from second spot to the top continues with little movement around Benjamin Sesko or Viktor Gyokeres. Here are the tales to keep an eye on from in and around the Emirates. Arsenal have confirmed the £5m signing of keeper Kepa Arrizabalaga from Chelsea . The Gunners have swooped for the Spain international who is set to become back-up and competition for current No1 David Raya . Arsenal have activated a £5m buy-out clause in Kepa’s contract which means he leaves Chelsea for a bargain fee seven years after moving to Stamford Bridge for £71.6m which made him the most expensive keeper in the world . Kepa, 30, who has won 13 senior caps for Spain, spent last season on loan at Bournemouth but was open to the switch to Arsenal to give himself a fresh challenge. Arsenal are expected to confirm the signing of Real Sociedad midfielder Martin Zubimendi, who has agreed a £51m switch while Arsenal are still looking for a left winger and striker. Sporting Lisbon are confident of completing a €55m (£47.2m) deal with Crystal Palace for their defender Ousmane Diomande in the coming days – ensuring the Portuguese side are under even less pressure to sell coveted striker Viktor Gyokeres for a cut price. Arsenal and Manchester United have appeared at the front of the queue for Sweden star Gyokeres but Sporting have made it clear that they will not accept anything less than their £85m asking price for their top scorer. Brentford's director of football Phil Giles admits he's "happy" that Christian Norgaard could be about to move to Arsenal - presenting the Dane with the chance to add silverware to his CV. The Gunners remain in talks to land the midfielder as they look to bolster their own ranks. Giles told Sky Sports : "Arsenal approached us in the last two weeks about Christian. I think it's fair to say it's more likely to happen than not. We have to go through the full process, tick all the boxes and then we'll see at the end of it. "He's been a fantastic player than us, unbelievable. I'm actually happy for him with the opportunity at this stage, 31, at this stage of his career to have an opportunity to go and try win some trophies.” Join our new WhatsApp community and receive your daily dose of Mirror Football content. We also treat our community members to special offers, promotions, and adverts from us and our partners. If you don't like our community, you can check out any time you like. If you're curious, you can read our Privacy Notice.