A down-the-hole hammer drill assembly having an axially forward cutting end and an axially rearward attachment end for coupling to a drill string, the assembly comprising: a drill bit positioned at the cutting end having a cutting head and a shank, a radially outward facing part of the shank comprising first retaining connections; an elongate casing to provide a housing for a piston capable of shuttling back and forth axially to strike a rearward anvil end of the shank; an annular drive sub provided at an axially forward end of the casing, the shank accommodated and extending axially through the drive sub, a radially outward facing part of the drive sub comprising second retaining connections; a retaining sleeve positioned around and extending axially between the respective part of the shank and the drive sub, the sleeve comprising third retaining connections positioned at a forward end of sleeve and fourth retaining connections positioned at a rearward end of sleeve to cooperatively engage respectively the first and second retaining connections to axially couple the drill bit to the drive sub; characterised in that: the first and third connections are configured to disengage one another axially and allow axial decoupling of the drill bit from the sleeve via an axially forward movement of the drill bit relative to drive sub; the second and forth connections are configured to disengage one another axially and allow axial decoupling of the sleeve from the drive sub via an axially forward movement of the sleeve relative to the drive sub; such that the axial coupling of the drill bit to the drive sub is provided exclusively via the engagement between the respective first and third and second and forth retaining connections. a drill bit positioned at the cutting end having a cutting head and a shank, a radially outward facing part of the shank comprising first retaining connections; an elongate casing to provide a housing for a piston capable of shuttling back and forth axially to strike a rearward anvil end of the shank; an annular drive sub provided at an axially forward end of the casing, the shank accommodated and extending axially through the drive sub, a radially outward facing part of the drive sub comprising second retaining connections; a retaining sleeve positioned around and extending axially between the respective part of the shank and the drive sub, the sleeve comprising third retaining connections positioned at a forward end of sleeve and fourth retaining connections positioned at a rearward end of sleeve to cooperatively engage respectively the first and second retaining connections to axially couple the drill bit to the drive sub; characterised in that: the first and third connections are configured to disengage one another axially and allow axial decoupling of the drill bit from the sleeve via an axially forward movement of the drill bit relative to drive sub; the second and forth connections are configured to disengage one another axially and allow axial decoupling of the sleeve from the drive sub via an axially forward movement of the sleeve relative to the drive sub; such that the axial coupling of the drill bit to the drive sub is provided exclusively via the engagement between the respective first and third and second and forth retaining connections. the first and third connections are configured to disengage one another axially and allow axial decoupling of the drill bit from the sleeve via an axially forward movement of the drill bit relative to drive sub; the second and forth connections are configured to disengage one another axially and allow axial decoupling of the sleeve from the drive sub via an axially forward movement of the sleeve relative to the drive sub; such that the axial coupling of the drill bit to the drive sub is provided exclusively via the engagement between the respective first and third and second and forth retaining connections.