"There's no cause for alarm," the source, who spoke on condition of anonymity, told Reuters.
Buckingham Palace had no comment on the Mail report but the source said such all-staff meetings did occur occasionally.
The queen, who celebrated her 91st birthday last month, and Philip, who turns 96 next month, still regularly carry out official duties although they have cut back on their workload in recent years.
Elizabeth met Prime Minister Theresa May on Wednesday to formally agree to the dissolution of parliament ahead of June's election while Philip opened a new stand at Lord's Cricket Ground in central London.
/Reuters/
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