We continued to implement our strategy to grow, simplify and restructure the Group, announcing nine transactions to dispose of or close businesses since the start of 2013, making the total 52 since the start of 2011. Consistent with our commitment to adopt global standards, we continue to take steps to de-risk our business.
Reported profit before tax ('PBT') for the first quarter of 2013 ('1Q13') was US$8.4bn, up 95% compared with the first quarter of 2012 ('1Q12'). This included adverse movements of US$0.2bn on the fair value of our own debt (1Q12: US$2.6bn) and gains of US$1.1bn from disposals and the reclassification of an associate (1Q12: US$0.2m).
Underlying PBT for 1Q13 was US$7.6bn, up 34% compared with 1Q12. This primarily reflected higher revenue of US$0.8bn and lower loan impairment charges of US$0.9bn, with a notable improvement in our US Consumer and Mortgage Lending ('CML') portfolio.
Underlying revenue included a net gain of US$0.6bn on completion of the sale of our remaining shareholding in Ping An and a US$0.5bn favourable debit valuation adjustment on derivative contracts. Remaining revenue was broadly unchanged. We achieved revenue growth in key areas including residential mortgages and Commercial Banking in both our home markets of Hong Kong and the UK, and Financing and Equity Capital Markets.
Underlying operating expenses were down 2% compared with 1Q12, reflecting lower charges in respect of UK customer redress programmes and a reduction in restructuring costs. We achieved US$0.4bn of additional sustainable cost savings during the quarter.
Underlying cost efficiency ratio improved to 53.2% in 1Q13 from 56.9% in 1Q12.
Core tier 1 capital ratio was 12.7% at 31 March 2013, up from 12.3% at 31 December 2012.