Aug 12 (Reuters) - London"s FTSE 100 closed lower on Thursday withRio Tinto weighing the most as it traded ex-dividend, while insurer Aviva topped the blue-chip index on strong first-half earnings. The FTSE 100 (.FTSE) fell 0.4% withRio Tinto (RIO.L) slipping 5.5% as it traded ex-dividend, after logging record half-year earnings last month. Oil majors BP (BP.L) and Royal Dutch Shell (RDSa.L)were also among the top drags on the FTSE after the International Energy Agency said the spread of the Delta variant of the coronavirus would slow the recovery of global oil demand. Insurer Aviva (AV.L) rose 3.5% and was the top gainer on the FTSE 100 after it reported a 17% rise in first-half operating profit and said it would return at least 4 billion pounds ($5.55 billion) to shareholders. read more The domestically focused mid-cap index (.FTMC) was flat. Cineworld (CINE.L) was the best performer on the index after outlining plans for a U.S. listing. read more Despite a volley of strong second-quarter earnings, the FTSE 100 has lagged its developed world in recent months due to having lower exposure to technology stocks, which tend to be more resilient to virus-related disruptions. But the midcap index, which is trading near record highs, has benefited from optimism over an economic recovery in Britain. Britain"s economy grew by a faster-than expected 1.0% in June, boosted by the huge services sector, against a Reuters poll of economists that pointed to a monthly growth of 0.8%. read more "While the headline UK GDP numbers show growth, we are still a long way from pre-pandemic levels with only government spending rising at good levels. But that cannot be said for the level of consumer spending, which is affecting investor sentiment to some extent," said Stefan Koopman, a senior market economist at Rabobank. Stock Spirits (STCK.L) surged 43.7% after the spirit maker agreed to a takeover by funds affiliated to private equity firm CVC in a deal valuing it at 767 million pounds ($1.1 billion). read more