The aircraft took off from London Gatwick on runway 08R at 12:30 hrs. Just after lift-off, at a height estimated to have been not more than 50 feet agl and just before the landing gear was retracted, a wheel was seen to fall to the ground by an eyewitness. Neither the operating crew nor the ATC tower controller were aware of this event until the eyewitness telephoned ATC about one minute after it had occurred. The tower controller then informed the commander that the aircraft appeared to have lost a wheel. The commander requested a visual inspection of his landing gear and was given radar directions for an extended right-hand circuit to bring his aircraft past the ATC tower at a height of 200 feet. Meanwhile, airport vehicles inspected the runway for debris and located the wheel, which had bounced along the north side of the runway and passed just north of the ILS localiser aerial, before coming to rest near the airport boundary fence. The commander was advised that the wheel had been identified as one from the main landing gear, and visual inspection of the aircraft during its fly-past by ATC indicated that the inner rear wheel (No. 6) of the left main bogie was missing. The aircraft safely returned to LGW. Inspection of the outer bearing showed that it had ‘burned up’ . This condition can result from inadequate bearing lubrication, which can occur due to insufficient quantity of lubricant to maintain a lubricant film, or due to the lubricant used not being capable of maintaining a proper film thickness for the bearing speeds and loads involved.