Iona has occupied its self-created niche of Christian progressive Celtic-rock with distinction for some twenty years, and Live in London offers a sustained taste of the Scottish quintet’s blend of ancient folk forms and contemporary sounds. Singer Joanne Hogg projects an inviting earth mother-like presence, easily shifting from mystical reveries into more forceful exhortations. The music here is richly evocative, lent character by Dave Bainbridge’s piercing lead guitar and Troy Donockley’s haunting uilliann pipes. “Flight of the Wild Goose” and “Wind Off the Lake” show off the band’s debt to ‘70s prog-rock (especially Renaissance), while “Encircling” bears traces of World Music influences. A billowing rendition of “Treasure” and a stirring take of “Strength” display their delicate way with spiritual themes, as well as their ability to write compact, hook-laden tunes when they choose. A highpoint here is a joyous version of “Castlerigg/Reels,” a medley that inspires spontaneous highland dancing. In concert, Iona’s sonic excursions take on heroic proportions, redolent of brooding moors and misty lakes.