1. **State the problem:** Factorise fully the expression $wy - y - 1 + w$. 2. **Group terms:** Group the terms to find common factors: $$wy - y - 1 + w = (wy - y) + (w - 1)$$ 3. **Factor out common factors in each group:** $$= y(w - 1) + 1(w - 1)$$ 4. **Factor out the common binomial factor:** $$= (w - 1)(y + 1)$$ 5. **Final answer:** The fully factorised form is $$ (w - 1)(y + 1) $$ This uses the distributive property and grouping method to factorise the expression.