A £3.3m treehouse, billed as the largest in Europe, has been opened at the Alnwick Garden by the Duchess of Northumberland.

The structure, which stretches 60ft high and features 4,000ft2 of suspended satellite walkways, was built using a wide range of timber products, including Canadian cedar, Siberian larch, Scandinavian redwood, English and Scots pine, plus glulam beams made in France.

John Harris, author of “Treehouses, a practical and inspirational guide” designed the treehouse, which was built by Sir Robert McAlpine Ltd. The 6,000ft2 structure is intended to offer “safely dangerous” play for children regardless of age or ability.