Modern slavery and immigration issues

Gary Craig says a Guardian article on modern slavery was a welcome addition to the literature. Your article “ The cannabis plants were more valuable than my life” (Journal, 26 July) was a welcome addition to the literature on modern slavery. Two points in it need addressing, however. The article commented that official estimates of the numbers of those in slavery in the UK are around 13,000. This estimate is an old one, long overtaken by more recent data and it would be good to move