The power of T cells to eradicate haematologic (and some non-haematologic) cancers has been demonstrated as a graft versus tumour (GVT) effect in the setting of allogeneic transplant for over 50 years. That power has been more recently captured in the form of adoptive cellular (CAR-T and NK cell) therapy generated as autologous product and now with emerging allogeneic sources. Currently, allogeneic transplantation represents the most widely applied (30,000 annually per year) and effective anti-cancer immunotherapy (3 year relapse free survival >50%). To date the induction and efficacy of allogeneic GVL has largely been concentrated on the intensity of the pre-transplant conditioning regimen intensity and factors associated with donor lymphocytes fitness (such as donor age). Increasingly, the immunomodulating effects of residual recipient immunity, either systemically or within the tumour micro-environment specifically have been recognised as important and potentially modifiable governors of donor lymphocyte engraftment and subsequent GVL effect. Recent findings indicates that novel targeted therapies including Ruxolitinib, Venetoclax and Flt3-inhibitors may be utilised to modify recipient immunity in order to promote the speed and efficacy of allogeneic GVL whilst limiting the onset of GVHD. Similarly, exploration of mechanisms of disease progression post-allogeneic transplantation (particularly in the setting of AML) have provided insights into optimal post-transplant strategies to prevent or treat relapse through recipient immune modulation.