London's seven-day run of gains is under threat as blue chips are struggling in the early exchanges.Barclays is lower after it confirmed Bob Diamond, head of its investment banking arm, Barclays Capital, will take over as chief executive when John Varley steps down at the end of March next year. Diamond, who's been running the division since 1997 when it was BZW, becomes president and deputy group chief executive at the beginning of next month.Tullow Oil is going well again after the vague bid talk yesterday that mentioned a £20 per share price. British Airways is also in demand as investors seemingly approve chief Willie Walsh's world domination plan. Costa Coffee and Premier Inns owner Whitbread said like for like (LFL) sales growth has accelerated since June. Year on year sales growth in the 24 weeks to 19 August was 7.9%, up from 7.6% in the 13 weeks to 3 June.Good sales of food through its managed outlets are keeping pub operator and brewer Greene King on track. After 18 weeks to 5 September, like-for-like sales at Greene King Retail were up by 4.4% and sales at Scottish arm Belhaven 3.3% ahead.Online grocery distributor Ocado's first figures since its troubled listing in July showed strong growth with gross sales up 29.5% to £126.5m for the 12 weeks to 8 August, though the size of the average order declined again. Equipment rental group Ashtead trumped the market's profit expectations handsomely in the first quarter of its financial year. Underlying profit before tax in the three months ended 31 July was £11.9m, up 35% (18% at constant exchange rates) from £8.8m in the company's first quarter of 2009. That figure beat the most optimistic broker forecast of £7.4m.Struggling social housing maintenance group Connaught has asked that its shares be suspended as its financial situation becomes ever more precarious. It doesn't think it will be able to prise additional funds from its lenders and, although it's still talking to other parties, admits "the ability to provide an adequate solution to the funding issues the group faces has become increasingly uncertain". Legacy software specialist Micro Focus has appointed former Morse chief executive Mike Phillips as its new Chief Financial Officer. Phillips replaces Nick Bray and starts at Micro Focus on 4 October. Office products wholesaler DS Smith has been trading in line with expectations in its new financial year with volume growth seen throughout the group. Reporting on trading since 1 May, the first quarter of the company's financial year, the company said volume growth has been led by its Fast Moving Consumer Goods section. Gem Diamonds has pulled another huge rough diamond from its Let?eng mine in Lesotho. The 196 carat rough white diamond was recovered on 24 August 2010. It is expected to achieve a substantial price per carat as preliminary examinations indicate it could produce top colour and top clarity polished diamonds, Gem said.