The messages arrive at all hours of the day and night, the vibration of a mobile phone signalling that another life hangs by a thread in Aleppo.

For the renowned British trauma surgeon David Nott and other doctors in London, Seattle, Washington and West Virginia, the Russian-backed onslaught on the city has been a daily reality.

They are a loose network of doctors who provide real-time medical support, often via WhatsApp and Skype internet services, to the desperately overstretched and sometimes dangerously inexperienced medical staff in the besieged areas of Syria.

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