The soprano's journey will begin as she is waved off at midday from London's Coliseum, home of the ENO, the day after her opening concert at Cadogan Hall in Chelsea (13 May). It will be "a longish first day", she says, as she marches "21 miles to Windsor for some sleep". From there she'll walk to Berkeley Castle in Gloucestershire (20 May), then on to the Cardiff Millennium Centre for two concerts (22 and 23 May). Walking on to Harewood House, near Leeds (13 June) - "through the Peak District, which will be lovely", she will then head back to London - "singing at concerts all the way".
Her vast repertoire includes well-loved arias such as "Softly Awakes My Heart" (Samson et Dalila) and "One Fine Day" (Madama Butterfly), along with "some lighter songs" by Ivor Novello.
Harries - whose career highlight was at Glyndebourne in 2004 in the dramatic role of the Kostelnicka in Jenufa - began her career relatively late, at 32. Her lucky break, as a Flower Maiden in Parsifal, at WNO in 1983 led to her being offered another role there - Leonore in Fidelio. "From then on, I've been working all over the world."
Although it may be a long road for Harries to raise enough money for those "who fall on hard times because of injury or illness" at the ENO and WNO, she enjoys long-distance walking. "I always have this urge to keep walking to see what is over the next horizon."
Tour begins 13 May (www.eno.org/operawalk)