There is provided a method of inserting casing into a borehole. The method comprises the steps of running a first section of casing into a pre-drilled borehole;underreaming under the in-place first section of casing using a standard underreamer and bit; running a second section of casing through the first section of casing with an expandable reamer shoe (1); and reaming down the borehole by rotation and/or reciprocation of the expandable reamer shoe (2) to an expected size.