Boris Johnson is to head to Singapore, in the latest of his post-prime ministerial travels, as the keynote speaker at a conference on blockchain. The former prime minister, who pulled out of the race to replace Liz Truss last week and is still the MP for Uxbridge and South Ruislip, will deliver the keynote address speech at the International Symposium on Blockchain Advancements on 2 December. Blockchain technology is used to provide a secure way of making and recording transactions, most commonly for the cryptocurrency bitcoin. Dick Cheney, the former US vice-president, is also speaking at the conference. The conference website says it “aims to guide the first step in migrating to the digital economy by provoking meaningful questions and discussions that will enable all of us, builders and consumers alike, to cut through the blockchain hype and grasp a realistic view of the emerging trends and needs, and to provide a technical blueprint for innovative solutions”. In September Johnson was paid £130,000 to give a speech at the Council of Insurance Agents and Brokers in Colorado, during which he joked about sharing the French president Emmanuel Macron’s “fancy” wine with Angela Merkel. On Tuesday, Johnson told Sky News that he will be “very happy” to go to the Cop27 climate summit after being “invited by the Egyptians”. Asked if Rishi Sunak should attend too, he said the new prime minister will have a “massive amount to do”, adding: “I happen to have a particular interest.” Two government sources told the Guardian that Sunak was now planning to attend the conference, after being accused of displaying a “failure of leadership”. But No 10 said the decision was still “under review”. Johnson told Sky it had become “unfashionable” to talk about Cop26, which he hosted in Glasgow last year. Asked if he felt more appreciated on the world stage, Johnson added: “I have an absolute passionate belief that the war in Ukraine, Putin’s act of aggression is something we shouldn’t accept. I think I can continue to campaign for Ukraine and that’s what I’m going to do.” Speaking to Sky from the Imperial War Museum, Johnson also said Vladimir Putin would be “crazy” to use a nuclear weapon in Ukraine, claiming the move would “immediately tender Russia’s resignation from the club of civilised nations”.