An internal combustion engine including: an engine body, a chamber body defining a pre-combustion chamber, a pipe, and a seal; the engine body defining: a combustion chamber, a cavity communicating with the combustion chamber, and a passageway communicating with the cavity; the pipe being arranged to supply fuel gas to the pre-combustion chamber in use; the chamber body being installed in the cavity of the engine body with the pre-combustion chamber in fluid communication with the combustion chamber of the engine; the pipe being installed in the passageway of the engine body in fluid communication with the pre-combustion chamber of the chamber body; characterised in that the seal includes a wall, the wall surrounding an interior space and including first and second portions (43, 44); the interior space opening through the wall at first, second and third openings (50, 60, 70); the first portion extending between the first and second openings (50, 60), the second portion extending between the third opening and the first portion; the first portion including: a first sealing region arranged between the first opening and the second portion, and a second sealing region arranged between the second opening and the second portion; each of the first and second sealing regions (51, 61) being configured to sealingly engage the chamber body, the chamber body being received in the interior space to extend through the first and second sealing regions (51, 61); the second portion including a third sealing region arranged between the third opening and the first portion, the third sealing region being configured to sealingly engage the pipe, the pipe being received in the interior space to extend through the third sealing region in fluid communication with the pre-combustion chamber of the chamber body. an engine body, a chamber body defining a pre-combustion chamber, a pipe, and a seal; the engine body defining: a combustion chamber, a cavity communicating with the combustion chamber, and a passageway communicating with the cavity; the pipe being arranged to supply fuel gas to the pre-combustion chamber in use; the chamber body being installed in the cavity of the engine body with the pre-combustion chamber in fluid communication with the combustion chamber of the engine; the pipe being installed in the passageway of the engine body in fluid communication with the pre-combustion chamber of the chamber body; a combustion chamber, a cavity communicating with the combustion chamber, and a passageway communicating with the cavity; the pipe being arranged to supply fuel gas to the pre-combustion chamber in use; the chamber body being installed in the cavity of the engine body with the pre-combustion chamber in fluid communication with the combustion chamber of the engine; the pipe being installed in the passageway of the engine body in fluid communication with the pre-combustion chamber of the chamber body; characterised in that the seal includes a wall, the wall surrounding an interior space and including first and second portions (43, 44); the interior space opening through the wall at first, second and third openings (50, 60, 70); the first portion extending between the first and second openings (50, 60), the second portion extending between the third opening and the first portion; the first portion including: a first sealing region arranged between the first opening and the second portion, and a second sealing region arranged between the second opening and the second portion; each of the first and second sealing regions (51, 61) being configured to sealingly engage the chamber body, the chamber body being received in the interior space to extend through the first and second sealing regions (51, 61); the second portion including a third sealing region arranged between the third opening and the first portion, the third sealing region being configured to sealingly engage the pipe, the pipe being received in the interior space to extend through the third sealing region in fluid communication with the pre-combustion chamber of the chamber body. the seal includes a wall, the wall surrounding an interior space and including first and second portions (43, 44); the interior space opening through the wall at first, second and third openings (50, 60, 70); the first portion extending between the first and second openings (50, 60), the second portion extending between the third opening and the first portion; the first portion including: a first sealing region arranged between the first opening and the second portion, and a second sealing region arranged between the second opening and the second portion; a first sealing region arranged between the first opening and the second portion, and a second sealing region arranged between the second opening and the second portion; each of the first and second sealing regions (51, 61) being configured to sealingly engage the chamber body, the chamber body being received in the interior space to extend through the first and second sealing regions (51, 61); the second portion including a third sealing region arranged between the third opening and the first portion, the third sealing region being configured to sealingly engage the pipe, the pipe being received in the interior space to extend through the third sealing region in fluid communication with the pre-combustion chamber of the chamber body.