A generally tubular drill string has a conductive path over a plurality of drill pipe section (10). Each drill pipe section has a first end and a second end, and a wall, and the first end has a first radial sealing surfaces (11) and the second end has a corresponding second radial surfaces (59), such that when the first or second end of one drill pipe section is engaged with the second or first end respectively of another drill pipe section, at least one seal is formed. The drill pipe includes at least one conductor (21) disposed inside it, this conductor being connected to a first contact means at the first end and a corresponding contact means at the second end of each drill pipe section. Ingress protection means (240) are provided to protect the contact means from ingress from inside or outside of the drill pipe section. The ingress protection means comprises a sealed volume surrounding the contact means.