Drilling apparatus for countersinking a predrilled hole formed in a part (2, 100), the predrilled hole being from a first side of the part (2, 100) to a second side of the part (2, 100), the first side being opposite to the second side, the apparatus comprising: a first robot; a first member coupled to the first robot; a drilling tool coupled to the first robot; a second robot; and a second member coupled to the second robot; wherein the apparatus is arranged to press the members (30, 52) against the opposite first and second sides of the part (2, 100) so as to hold the part (2, 100) and prevent deflection of at least a portion of the part (2, 100) in which the predrilled hole is formed; and the first member and the drilling tool are arranged such that the drilling tool countersinks the predrilled hole to a predetermined depth while the members (30, 52) are pressed against the part (2, 100), the countersinking being from the side of the part (2, 100) pressed against by the first member, the apparatus further comprising: a surface measurement system configured to measure a surface of the part (2, 100) at a plurality of points proximate to and surrounding the predrilled hole; and a normalisation processor operatively coupled to the surface measurement system; wherein the normalisation processor is configured to, using the measurements of the surface, determine an action for performance by at least part of the apparatus; the action is such that, if it were to be performed by the at least part of the apparatus, the drilling tool would be positioned at a predetermined angle relative to the measured surface of the part (2, 100); and the at least part of the apparatus is arranged to perform the action before countersinking. a first robot; a first member coupled to the first robot; a drilling tool coupled to the first robot; a second robot; and a second member coupled to the second robot; wherein the apparatus is arranged to press the members (30, 52) against the opposite first and second sides of the part (2, 100) so as to hold the part (2, 100) and prevent deflection of at least a portion of the part (2, 100) in which the predrilled hole is formed; and the first member and the drilling tool are arranged such that the drilling tool countersinks the predrilled hole to a predetermined depth while the members (30, 52) are pressed against the part (2, 100), the countersinking being from the side of the part (2, 100) pressed against by the first member, the apparatus further comprising: a surface measurement system configured to measure a surface of the part (2, 100) at a plurality of points proximate to and surrounding the predrilled hole; and a normalisation processor operatively coupled to the surface measurement system; wherein the normalisation processor is configured to, using the measurements of the surface, determine an action for performance by at least part of the apparatus; the action is such that, if it were to be performed by the at least part of the apparatus, the drilling tool would be positioned at a predetermined angle relative to the measured surface of the part (2, 100); and the at least part of the apparatus is arranged to perform the action before countersinking. a surface measurement system configured to measure a surface of the part (2, 100) at a plurality of points proximate to and surrounding the predrilled hole; and a normalisation processor operatively coupled to the surface measurement system; wherein the normalisation processor is configured to, using the measurements of the surface, determine an action for performance by at least part of the apparatus; the action is such that, if it were to be performed by the at least part of the apparatus, the drilling tool would be positioned at a predetermined angle relative to the measured surface of the part (2, 100); and the at least part of the apparatus is arranged to perform the action before countersinking.