Mayor of Southwark Cllr Catherine Rose will join in the merriment too as she officially switches on the Christmas tree lights at 5.30pm.
Upbeat jazz from the Holloway Allstars, led by double bassist Amy Baldwin, will get the party swinging.
While crafty folk can put together a festive wreath using greenery from BOST's gardens. Children are very welcome and can try their hand at a ribbon scrap Christmas tree make.
Mulled wine and other festive refreshments will be on sale to raise funds for the trust's much-loved green spaces and volunteer projects across north Southwark.
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