The Met Police has told cyclists involved in the 'critical mass' procession to keep moving and keep south of the Thames.
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A former Royal Marine who has recently been engaged has been killed in a climbing accident in the French Alps.
Through the day we'll see plenty of sunny spells but there will be a risk of showers too as they filter down from the northwest.
Pilots say they are rostered in 'illegally' and feel fatigued from working too many hours.