The FTSE 100 traded flat to slightly higher on Tuesday, extending gains for a third session, supported by strong corporate earnings. AstraZeneca rose as much as 2% after reporting better-than-expected second-quarter results, driven by strong sales of its cancer drugs. Barclays also started higher, buoyed by news of a 1 billion GBP share buyback after a solid performance in its trading and UK corporate divisions. However, shares later slipped 0.6% as analysts pointed out that overall revenue missed expectations, with weakness in the US business and currency headwinds raising questions. Elsewhere, Greggs posted a 7% rise in first-half revenue, despite softer footfall due to unusually hot weather. Investors remain cautious ahead of major central bank decisions later in the week.