An assembly comprising: a gas turbine engine comprising: a fan section delivering air into a main compressor section, said main compressor section including a first compressor section and a second compressor section operating at a higher pressure than the first compressor section, said main compressor section compressing air and delivering air into a combustion section where the air is mixed with fuel and ignited to generate products of combustion that are passed over a turbine section to drive said fan section and main compressor sections; an environmental control system comprising: a higher pressure tap at a higher pressure location of the main compressor section; a lower pressure tap at a lower pressure location of the main compressor section, the lower pressure location being at a lower pressure than said higher pressure location; and a turbocompressor including a compressor section configured to be driven by a turbine section of the turbocompressor, wherein the lower pressure tap is in communication with the compressor section of the turbocompressor and the higher pressure tap is in communication with the turbine section of said turbocompressor such that air from the higher pressure tap drives the turbine section to in turn drive the compressor section of the turbocompressor, and a combined outlet of said compressor section and said turbine section of said turbocompressor intermixing and passing air downstream to be delivered to an aircraft use; and a pylon supporting the engine, characterised in that: the pylon defines a lowermost surface and the higher pressure tap extends above a plane including the lowermost surface, the higher pressure tap comprises a double wall tube above the plane for preventing leakage from impinging on a portion of the pylon. a gas turbine engine comprising: a fan section delivering air into a main compressor section, said main compressor section including a first compressor section and a second compressor section operating at a higher pressure than the first compressor section, said main compressor section compressing air and delivering air into a combustion section where the air is mixed with fuel and ignited to generate products of combustion that are passed over a turbine section to drive said fan section and main compressor sections; an environmental control system comprising: a higher pressure tap at a higher pressure location of the main compressor section; a lower pressure tap at a lower pressure location of the main compressor section, the lower pressure location being at a lower pressure than said higher pressure location; and a turbocompressor including a compressor section configured to be driven by a turbine section of the turbocompressor, wherein the lower pressure tap is in communication with the compressor section of the turbocompressor and the higher pressure tap is in communication with the turbine section of said turbocompressor such that air from the higher pressure tap drives the turbine section to in turn drive the compressor section of the turbocompressor, and a combined outlet of said compressor section and said turbine section of said turbocompressor intermixing and passing air downstream to be delivered to an aircraft use; and a fan section delivering air into a main compressor section, said main compressor section including a first compressor section and a second compressor section operating at a higher pressure than the first compressor section, said main compressor section compressing air and delivering air into a combustion section where the air is mixed with fuel and ignited to generate products of combustion that are passed over a turbine section to drive said fan section and main compressor sections; an environmental control system comprising: a higher pressure tap at a higher pressure location of the main compressor section; a lower pressure tap at a lower pressure location of the main compressor section, the lower pressure location being at a lower pressure than said higher pressure location; and a turbocompressor including a compressor section configured to be driven by a turbine section of the turbocompressor, wherein the lower pressure tap is in communication with the compressor section of the turbocompressor and the higher pressure tap is in communication with the turbine section of said turbocompressor such that air from the higher pressure tap drives the turbine section to in turn drive the compressor section of the turbocompressor, and a combined outlet of said compressor section and said turbine section of said turbocompressor intermixing and passing air downstream to be delivered to an aircraft use; and a higher pressure tap at a higher pressure location of the main compressor section; a lower pressure tap at a lower pressure location of the main compressor section, the lower pressure location being at a lower pressure than said higher pressure location; and a turbocompressor including a compressor section configured to be driven by a turbine section of the turbocompressor, wherein the lower pressure tap is in communication with the compressor section of the turbocompressor and the higher pressure tap is in communication with the turbine section of said turbocompressor such that air from the higher pressure tap drives the turbine section to in turn drive the compressor section of the turbocompressor, and a combined outlet of said compressor section and said turbine section of said turbocompressor intermixing and passing air downstream to be delivered to an aircraft use; and a pylon supporting the engine,