A watching brief was conducted by the Cambridge Archaeological Unit of work in advance of the construction of a rear extension to 21 Magdalene Street, Cambridge. The preparation involved the demolition of the existing yard and outbuildings, the removal of the concrete footing of these structures and the excavation of two foundation trenches as footings. The trenches were hand dug by the developers to a depth of c. 0.90m and a width of c. 0.80m. Features and deposits were observed in section only; consequently recording was not as extensive as it might otherwise have been. Present day Magdalene Street follows the course of the important southeasterly route into Cambridge which spans the River Cam at a narrow crossing point. The site lies some 200m from the Castle Mound, centre of the old upper town, and falls therefore in an area of considerable archaeological interest.