To tread the streets of Viking Dublin with entertaining commentary along the way, Hidden Dublin Walks runs walking tours of the city, relaying its often-brutal beginnings.

BBC: Dublin's Viking heritage

The walks prompted vivid memories which he included in his blog Walking on Planet C which is a frank and often uncomfortable account of life in the shadow of a potentially fatal illness.

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The guides of the independent London Walks company have earned the city's premiere professional qualification for walking tours, the Blue Badge.

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