By Chris Dorrell Higher interest rates continued to provide a welcome tailwind for Investec, as the firm upped its dividend on the back of higher annual profit figures. Operating income at the bank rose by five per cent in the year to £2.1bn, up from £2.0bn last year. The revenue boost came as interest income rose 5.6 per cent in the year, thanks to “higher global interest rates”. Non-interest income also increased, with net fee and commission income rising by nearly five per cent. This helped adjusted operating profit rose eight per cent year on year to £884.5m, up from £818.7m last year. Inv…