A gas turbine engine comprising: a high pressure spool; a low pressure spool comprising a compressor fixedly connected to a turbine via a spool shaft; a fan drive gear system that includes a bearing; a fan shaft connected through the fan drive gear system to the low pressure spool; a pump system for lubricating the bearing, the pump system comprising: a main pump driven by the high pressure spool and fluidically connected to supply lubricating liquid to the bearing through a main supply passage; an auxiliary pump connected to the gear system such that in use the auxiliary pump rotates whenever the gear system rotates, wherein the auxiliary pump is fluidically connected to supply lubricating liquid to the bearing through an auxiliary supply passage and to a reservoir through an auxiliary scavenge passage; and an auxiliary valve fluidically connected to the auxiliary supply passage, for transferring lubricating liquid from the auxiliary pump to the bearing when a pressure in the auxiliary supply passage downstream of the auxiliary valve is less than a particular threshold, and for transferring lubricating liquid from the auxiliary pump to the reservoir when the pressure in the auxiliary supply passage downstream of the auxiliary valve is greater than the particular threshold, wherein the main pump is arranged to pump lubricating liquid to the bearing when the high pressure spool is rotating at an operating speed, and the auxiliary pump is arranged to pump lubricating liquid to the bearing when the high pressure spool is rotating below the operating speed. a high pressure spool; a low pressure spool comprising a compressor fixedly connected to a turbine via a spool shaft; a fan drive gear system that includes a bearing; a fan shaft connected through the fan drive gear system to the low pressure spool; a pump system for lubricating the bearing, the pump system comprising: a main pump driven by the high pressure spool and fluidically connected to supply lubricating liquid to the bearing through a main supply passage; an auxiliary pump connected to the gear system such that in use the auxiliary pump rotates whenever the gear system rotates, wherein the auxiliary pump is fluidically connected to supply lubricating liquid to the bearing through an auxiliary supply passage and to a reservoir through an auxiliary scavenge passage; and an auxiliary valve fluidically connected to the auxiliary supply passage, for transferring lubricating liquid from the auxiliary pump to the bearing when a pressure in the auxiliary supply passage downstream of the auxiliary valve is less than a particular threshold, and for transferring lubricating liquid from the auxiliary pump to the reservoir when the pressure in the auxiliary supply passage downstream of the auxiliary valve is greater than the particular threshold, wherein the main pump is arranged to pump lubricating liquid to the bearing when the high pressure spool is rotating at an operating speed, and the auxiliary pump is arranged to pump lubricating liquid to the bearing when the high pressure spool is rotating below the operating speed. a main pump driven by the high pressure spool and fluidically connected to supply lubricating liquid to the bearing through a main supply passage; an auxiliary pump connected to the gear system such that in use the auxiliary pump rotates whenever the gear system rotates, wherein the auxiliary pump is fluidically connected to supply lubricating liquid to the bearing through an auxiliary supply passage and to a reservoir through an auxiliary scavenge passage; and an auxiliary valve fluidically connected to the auxiliary supply passage, for transferring lubricating liquid from the auxiliary pump to the bearing when a pressure in the auxiliary supply passage downstream of the auxiliary valve is less than a particular threshold, and for transferring lubricating liquid from the auxiliary pump to the reservoir when the pressure in the auxiliary supply passage downstream of the auxiliary valve is greater than the particular threshold, wherein the main pump is arranged to pump lubricating liquid to the bearing when the high pressure spool is rotating at an operating speed, and the auxiliary pump is arranged to pump lubricating liquid to the bearing when the high pressure spool is rotating below the operating speed.