With little corporate news elsewhere to excite investors, the FTSE 100 Index eased 6.1 points to 5348.6 after an hour of trading.
HSBC - unchanged at 837p - is expected to unveil pre-tax profits of just over 10 billion US dollars (pounds 5bn) despite further writedowns at its US business and investments hit by the credit crunch.
The leading Footsie riser was telecoms group BT, 2.8p better at 174.1p after traders decided the stock looked oversold following last week's poorly-received interims.
Crude oil ticking up to 126 US dollars a barrel meanwhile helped BP and Royal Dutch Shell, up 7.5p to 528.75 and 23p to 1773p respectively, although falls for heavyweight miners offset these gains.
Second-tier stocks were helped by takeover interest. Imperial Energy led the FTSE 250 with a 9% rise, or 95p, to 1169p after confirming a second bid approach.
It was closely followed by pubs group Punch Taverns, up 3.5p to 44p, or 8%, on weekend reports of interest from private equity firm CVC.