1. A method of controlling fuel injection in an internal combustion engine having at least one cylinder with an associated fuel injector for performing injection events, wherein for each injection event a pulse width is determined with which the injector is kept open to spray a desired quantity of fuel, wherein when the quantity of fuel of a given fuel injection event is greater than a learning threshold, a split fuel injection is performed, whereby a first, low injection pulse and a second, complementary injection pulse are executed, and wherein data representative of at least one of a closing time and an opening time of the fuel injector is determined in respect of said first, low injection pulse and a learned correction value is elaborated based on at least one of said closing time and said opening time, said learned correction value being subsequently used for injection control, wherein said learning threshold is calibrated as a function of the pulse width for which the closing time is to be learned.