Estimates of small modular reactor (SMR) costs should be treated with scepticism until the first few of the mini-nuclear power plants have been built, a leading energy academic has warned. Professor Jim Watson of University College London (UCL) sounded the warning during a House of Commons energy security and net zero committee meeting. He said while large scale nuclear reactors, like EDF’s Hinkley C project, are not going to be delivered “very quickly and will always be expensive, the true costs of building SMRs will only be realised after they starting being built.