Professional standards applied and level of assurance We performed a limited assurance engagement in accordance with International Standard on Assurance Engagements Engagements other than Audits and Reviews of Historical Financial Information’ and, in respect of the CO2 emissions, in accordance with International Standard on Assurance Engagements 3410 – ‘Assurance engagements on greenhouse gas statements’ issued by the International Auditing and Assurance Standards Board.