| 1993-may | Ordered | Ordered  L12 HMS Ocean | |
| 1994-jun-30 | Laid down | Laid down L12 HMS Ocean Yard No 309 | |
| 1995-oct-11 | Launched | Launched L12 HMS Ocean | |
| 1998-sep-30 | Commissioned | Commissioned L12 HMS Ocean aka The Mighty O | |
| 1998-oct | Deployment | Deployment L12 HMS Ocean Operation Tellar Hurricane relief operations off central America, with Sea Kings of 845 NAS and Lynx and Gazelle of 847 NAS embarked. | |
| 2000-may | Deployment | Deployment L12 HMS Ocean Operation Palliser ordered off Freetown, Sierra Leone to support Operation Palliser and arrived on 14 May with 42 Commando RM, six Sea Kings of 846 NAS, two Lynx and two Gazelle from 847 NAS and two Chinooks from RAF 7 Sq embarked. Departed Freetown on 15 Jun. | |
| 2003-jan-16 | Deployment | Deployment L12 HMS Ocean Operation Telic to support combat operations in Iraq, standing off Kuwait, and embarked at least nine Sea Kings of 845 NAS plus six Lynx and six Gazelle of 847 NAS, together with 40 Commando RM. Left theatre on 28 May 2003 | |
| 2004-may-13 | Deployment | Deployment L12 HMS Ocean departed HMNB Devonport in company with HMS Albion, HMS Cornwall, HMS Sutherland, RFA Argus, RFA Fort George, RFA Fort Rosalie, RFA Sir Galahad, RFA Sir Tristram and RFA Oakleaf, as part of an Amphibious Task Group, for exercises with US Navy. Arrived Norfolk, VA on 28 May. | |
| 2005-sep | Aircraft | Aircraft L12 HMS Ocean supported a deployment of 656 Sq Apache to establish Maritime Interim Operational Capability | |
| 2006-oct-11 | Deployment | Deployment L12 HMS Ocean Operation Vela (Green Eagle) conduct of Exercise Green Eagle phase of Operation Vela, off Sierra Leone. Two Lynx AH.7 of 847 NAS embarked. | |
| 2007-sep | Refit | Refit L12 HMS Ocean 11 month upgrade refit at Babcock Marine at HMD Devonport, completed early Sep 2008. | |
| 2009-jun | Deployment | Deployment L12 HMS Ocean Departed HMNB Devonport for Caribbean anti-drug and maritime security deployment | |
| 2009-sep-05 | Homeport | Homeport L12 HMS Ocean present for Navy Days 2009, with 820 NAS Merlin HM.1 ZH863/11 aboard | |
| 2009-sep-18 | Port Visit | Port Visit L12 HMS Ocean visited Sunderland for 4 days, departed 21 Sep. 6x Lynx of 702 NAS and 2x Apache of 656 Sq embarked. | |
| 2010-mar-11 | Port Visit | Port Visit L12 HMS Ocean Arrived 11 March Rotterdam harbour after exercise Cold Response 10. No helicopters on board. Dep 15 March | |
| 2010-jun | Deployment | Deployment L12 HMS Ocean Departed HMNB Devonport for 5 month Atlantic deployment, returning 1 Nov 2010. | |
| 2010-jul | Deployment | Deployment L12 HMS Ocean Exercise Auriga 2010 Participated in the Amphibious component of Ex Auriga, with USS Kearsarge, HMS Albion and RFA Largs Bay, until Aug 2010. At least ZF121 / X embarked from the CHF. | |
| 2010-sep-09 | Port Visit | Port Visit L12 HMS Ocean visit to Rio de Janeiro for 3 days as part of a global deployment | |
| 2010-oct | Port Visit | Port Visit L12 HMS Ocean 4 day visit to Freetown, Sierra Leone, 10 years after her deployment on Operation Palliser. | |
| 2011-feb-11 | Port Visit | Port Visit L12 HMS Ocean visited Tyneside for 4 days | |
| 2011-apr-28 | Deployment | Deployment L12 HMS Ocean Operation Unified Protector Departed HMNB Devonport for 7 week work up, diverted to Mediterranean deployment for operations off Libya. 857 NAS detachment embarked in late May and arrived back at Culdrose on 27 Sep 2011. The deployment included first time combat operations from a maritime platform by the Army Attack Helicopter Force, where 3 (eventually 5) Apache AH.1 of 656 Squadron joined the ship. Returned to UK 9 Dec 2011. | |
| 2011-sep-24 | Port Visit | Port Visit L12 HMS Ocean Operation Unified Protector Alongside at Souda Naval Base, following end of UK Operation Ellamy air operations from the ship. | |
| 2012-may-18 | Port Visit | Port Visit L12 HMS Ocean 3 day visit to Hamburg, with Ship Open to Visitors and interoperability exercises with Sea Kings of MFG 5. | |
| 2012-jul-13 | Deployment | Deployment L12 HMS Ocean to Greenwich Reach as a maritime logistic hub in support of Police maritime security operations at London 2012 Olympic & Paralympic Games, until 11 Sep, when she departed on the midday tide. | |
| 2012-dec | Refit | Refit L12 HMS Ocean surface and low level air search radar Type 997 entered 10 Dock at HMD Devonport with Babcock for 15 month major upkeep and upgrade programme. Includes new Type 997 Artisan radar, 30mm guns, IT and environmental systems, with a new 20kt top speed. Came out of dry dock on 31 Jul 2013 and is due to complete 2014. | |
| 2014-jul-05 | Trials | Trials L12 HMS Ocean Sea trials after completing refit at Devonport | |
| 2014-nov-21 | Port Visit | Port Visit L12 HMS Ocean visit to Portsmouth | |
| 2015-mar-20 | Refit | Refit L12 HMS Ocean rejoined the fleet following refit after short re-commissioning ceremony at Devonport. | |
| 2015-apr-11 | Deployment | Deployment L12 HMS Ocean Exercise Joint Warrior 15-1 participated in JW 15-1. Embarked 4x Sea King HC.4 from 845 NAS on 14 Apr and also hosted 2x Longbow Apache and 2x Chinook. | |
| 2015-may-01 | Port Visit | Port Visit L12 HMS Ocean visit to Sunderland, departed 5 May. | |
| 2015-may-07 | Port Visit | Port Visit L12 HMS Ocean arrived at Greenwich on 7 May for VE Day celebrations. Departed 11 May. | |
| 2015-jun-05 | Deployment | Deployment L12 HMS Ocean BALTOPS 15 After assuming UK Flagship role role on 1 Jun, deployed to Baltic Sea for BALTOPS 2015. | |
| 2015-sep-29 | Deployment | Deployment L12 HMS Ocean Exercise Trident Juncture 2015 departed HMNB Devonport for 4 month Mediterranean deployment on multi-national Exercise Cougar 15. During mid-late Oct, participated in Exercise Trident Juncture 2015 in Mediterranean. | |
| 2015-dec-05 | Port Visit | Port Visit L12 HMS Ocean visited Gibraltar, with at least Merlins ZH836 and ZH850 embarked. | |
| 2016-sep-20 | Deployment | Deployment L12 HMS Ocean Joint Expeditionary Force (Maritime) 2016 departed HMNB Devonport for a 6 month Mediterranean and Middle East maritime security deployment, incluing a period as Flagship for CTF-50. Detachment of 820 NAS Merlin embarked which included ZH835 and ZH854. Returned to Plymouth 24 Mar 2017. | |
| 2017-jan-31 | Deployment | Deployment L12 HMS Ocean Exercise Unified Trident Flagship of CTF50 for multi-national Ex Unified Trident in Persian Gulf until 2 Feb. | |
| 2017-mar-04 | Port Visit | Port Visit L12 HMS Ocean visited Beirut from 4 Mar 2017 | |
| 2017-mar-09 | Port Visit | Port Visit L12 HMS Ocean visited Malta for weekend, on homeward leg of Middle East deployment | |
| 2017-aug-29 | Deployment | Deployment L12 HMS Ocean SNMG2 Departed HMNB Devonport for 4 month final deployment. Chinook ZH775 and Merlins of 845 NAS embarked; to become Flagship of NATO SNMG2 in Mediterranean. Returned 19 Dec 2017. | |
| 2017-sep-07 | Deployment | Deployment L12 HMS Ocean Hurricanes Irma, Jose and Maria Relief Operations Diverted from Mediterranean and ordered to Caribbean to assist in relief operations following Hurricane Irma and Hurricane Jose. HMS Duncan Flagship role extended deployment until relieved on station. | |
| 2017-sep-11 | Port Visit | Port Visit L12 HMS Ocean Hurricanes Irma, Jose and Maria Relief Operations Embarked 60 pallets of disaster relief and 200 pallets of aid consignments for Caribbean flown into RAF Gibraltar by 4x 18 Squadron Chinook, from RAF Odiham. | |
| 2017-sep-22 | Deployment | Deployment L12 HMS Ocean Hurricanes Irma, Jose and Maria Relief Operations Arrived British Virgin Islands, to contribute towards relief effort. | |
| 2017-sep-25 | Deployment | Deployment L12 HMS Ocean Hurricanes Irma, Jose and Maria Relief Operations Departed Anguilla to bring aid to the Commonwealth of Dominica, following Hurricane Maria. Withdrawn on 9 Oct. | |
| 2018-feb-17 | | L12 HMS Ocean UK MoD announced sale to Brazil, to replace the NAeL São Paulo. Deal also includes a refit at UK shipyard prior to delivery (expected Jun 2018). | |
| 2018-mar-27 | Decommissioned | Decommissioned L12 HMS Ocean decommissioned, with HM Queen present | |
| 2018-jun | Commissioned | Commissioned  A140 PHM Atlantico at UK HMD Devonport | |
| 2018-aug-01 | Deployment | Deployment A140 PHM Atlantico departed UK HMNB Devonport on delivery voyage to Rio de Janeiro | |
| 2018-aug-04 | Port Visit | Port Visit A140 PHM Atlantico arrived in Lisbon on delivery voyage from UK to Rio de Janeiro | |
| 2018-aug-23 | | A140 PHM Atlantico first Brazilian landings ( 1 UH-15 Super Cougar, 1 SH-16 Seahawk and 1 IH-6B Bell Jet Ranger III ) near Cabo Frio | |
Aircraft