A gas turbine engine comprising: a fan, a turbine section including a turbine rotor to drive said fan through a gear reduction module; an input shaft downstream of said turbine rotor including a flexible mount (126, 127) driving said gear reduction module, said input shaft being mounted within a bearing module, and said gear reduction module having a static structure mounted to an engine housing through the flexible mount (126, 127); and an oil supply system to supply oil into said gear reduction module, the oil supply system comprising: an oil tube to supply oil from said gear reduction module to said bearing module, said oil tube being received within an opening in said static structure, and in an opening in a housing for said bearing module, said oil tube extending through an assembly guide having a guide opening which is spaced away from an outer periphery of said oil tube, and said guide opening is intermediate said opening in said static structure, and said opening in said bearing housing, wherein said opening in said static structure, and said opening in said bearing housing both have a chamfer (130, 132) leading into said openings (118, 120) to allow said tube to pivot within each said opening (118, 120), and said guide opening (118, 120) is sized to be spaced from said outer periphery of said oil tube by an amount which will limit any pivoting movement of said oil tube such that it will be aligned with a portion of said chamfer (130, 132) into one of said openings (118, 120) in said static structure and said bearing housing to which it is being assembled; and characterised in that: said tube is provided with resilient seals at an outer periphery, wherein the opening receives one end of the tube having resilient seals, and the opening also receives an end of the tube having resilient seals to allow said tube to pivot within said openings (118, 120) in said static structure and said bearing housing. a fan, a turbine section including a turbine rotor to drive said fan through a gear reduction module; an input shaft downstream of said turbine rotor including a flexible mount (126, 127) driving said gear reduction module, said input shaft being mounted within a bearing module, and said gear reduction module having a static structure mounted to an engine housing through the flexible mount (126, 127); and an oil supply system to supply oil into said gear reduction module, the oil supply system comprising: an oil tube to supply oil from said gear reduction module to said bearing module, said oil tube being received within an opening in said static structure, and in an opening in a housing for said bearing module, said oil tube extending through an assembly guide having a guide opening which is spaced away from an outer periphery of said oil tube, and said guide opening is intermediate said opening in said static structure, and said opening in said bearing housing, wherein said opening in said static structure, and said opening in said bearing housing both have a chamfer (130, 132) leading into said openings (118, 120) to allow said tube to pivot within each said opening (118, 120), and said guide opening (118, 120) is sized to be spaced from said outer periphery of said oil tube by an amount which will limit any pivoting movement of said oil tube such that it will be aligned with a portion of said chamfer (130, 132) into one of said openings (118, 120) in said static structure and said bearing housing to which it is being assembled; and characterised in that: said tube is provided with resilient seals at an outer periphery, wherein the opening receives one end of the tube having resilient seals, and the opening also receives an end of the tube having resilient seals to allow said tube to pivot within said openings (118, 120) in said static structure and said bearing housing.