The high pressure \u201cheat dome\u201d that descended on Europe in late June<\/a> caused wind turbines to slow, gas power plants to falter, and the French nuclear plants exporting electricity to Britain to power down. Meanwhile, electricity demand for air conditioning and refrigeration units jumped as Britons attempted to stay cool.<\/p>\n The task of keeping the grid\u2019s electricity supplies stable during the June and July heatwaves was set against the backdrop of a political row, and a culture war<\/a> over Britain\u2019s ambitious clean energy targets and the cost of reaching net zero.<\/p>\n Earlier this month the shadow energy secretary, Claire Coutinho, told parliament that whistleblowers from within Neso had accused senior managers of being involved in a cover-up over the extent of the power system strain during record high temperatures in the UK and mainland Europe<\/a> in late June.<\/p>\n The accusations included the claim that control room staff were ordered by senior managers to forgo normal note-keeping to avoid creating a full audit trail of their efforts to stabilise the power system. Whistleblowers have also alleged that members of the corporate affairs team attempted to pressure operators to make decisions that would protect the organisation\u2019s reputation, Coutinho said.<\/p>\n The employees came forward because they were \u201cworried that the grid is becoming increasingly unmanageable\u201d and that senior bosses were \u201crisking blackouts to protect Neso\u2019s reputation\u201d, she said. \u201cIf true, this is nothing short of a scandal.\u201d<\/p>\n Last week, Neso said that it had brought in independent investigators from the law firm Eversheds Sutherland<\/a> to examine the accusations.<\/p>\n So what do we know about how the system operator handled the heatwave? The whistleblower allegations focus on the last week of June. It was a week that demonstrated that summer heatwaves can \u201cnow create system conditions traditionally associated with winter scarcity events\u201d, according to LCP Delta, a consultancy.<\/p>\n During that week, Neso issued a string of emergency measures to shore up Great Britain\u2019s electricity supplies, marking the first time these tools were used during a summer period. \u200bTo underline the challenge, figures this week showed<\/a> Neso spent almost \u00a3800,000 getting consumers to use less electricity than normal between mid-April and mid-July, according to the Financial Times.<\/p>\n Neso took emergency measures to shore up Great Britain\u2019s electricity supplies in the last week of June. Photograph: Tommaso Altamura\/Alamy<\/p>\n D\u200bespite these levers, the frequency of the grid \u2013 which Neso aims to keep at about 50Hz \u2013 fell to the edge of its operational limits of between 49.8Hz and 50.2Hz.<\/p>\n The operation range, which is used to prevent blackouts, remained under pressure for the better part of an hour on 23 June. The lowest recorded frequency was 49.66Hz, still well above the statutory lower limit of 49.5Hz.<\/p>\n However, a former \u200be\u200bmployee told the Guardian that the prolonged period of lower than usual frequency \u200bm\u200bay suggest that the system operator was running low on politically palatable options to address the strain on the grid before more serious interventions, such as disconnecting factories<\/a>, might have been needed.<\/p>\n \u201cWhen I saw the grid frequency data I thought it just couldn\u2019t be right because it was at the lower end of the operational limits for such a long time. A 0.2Hz change might not seem very large but in technical terms it represents a much greater vulnerability. At these levels there is a risk that something unexpected might happen which the system would be too strained to absorb,\u201d they said.<\/p>\n Neso has downplayed the concerns. Although the heatwave led to \u201csustained pressure on power systems\u201d and \u201ctight operating margins\u201d, \u200baccording to Craig Dyke, a Neso director, \u201cno customer demand was disconnected, frequency remained within statutory limits, the voltage stayed within limits and no lines or cables were overloaded\u201d.<\/p>\n In two instances in the last week of June, the system operator was forced to raise the alarm<\/a> over electricity supplies because of the impact of the heatwave, which scientists believe was more severe and more likely happen because of the climate crisis<\/a>.<\/p>\n This resulted in payments estimated to reach millions of pounds for just a few hours of emergency electricity generated by gas power plants, a leading cause of the atmospheric carbon emissions that are accelerating global heating.<\/p>\n skip past newsletter promotion<\/a>Free newsletter | Every weekday<\/p>\n Sign up to Business Today<\/p>\n Get set for the working day \u2013 we’ll point you to all the business news and analysis you need every morning<\/p>\n after newsletter promotion<\/p>\n Neso controllers are also understood to have breached the normal limits on trading power across the giant subsea power cables linking Great Britain\u2019s electricity system to generators in continental Europe \u201cseveral times\u201d across the week, according to analysts.<\/p>\n Neso controllers are understood to have breached the normal limits on trading power across the subsea power cables linking Great Britain\u2019s electricity system to generators in continental Europe. Photograph: Mint Images\/Getty Images\/Mint Images RF<\/p>\n The largest of these breaches occurred on 24 June, when Neso issued an emergency call for an additional 500MW of power capacity from the Netherlands through the BritNed power line, achieved by cutting Great Britain\u2019s exports. A similar emergency call was made to France.<\/p>\n Some market experts are wary about any suggestion that Great Britain may have experienced a blackout \u201cnear miss\u201d during the heatwave. \u200bBlackouts are extremely rare in the UK, and when they do occur they are the result of a confluence of unforeseen events<\/a>.<\/p>\n In 2025, Europe\u2019s worst blackout in 20 years<\/a> \u2013 across Spain, Portugal and parts of southern France \u2013 was blamed on multiple interacting factors that destabilised the grid\u2019s frequency. In 2019 there was a short-lived blackout<\/a> in the UK when a lightning strike caused two electricity generators more than 100 miles apart to disconnect from the grid in an \u201cextremely rare and unexpected event\u201d.<\/p>\n The risk to Neso\u2019s reputation from a potential near miss is significant, the former employee stressed. In a worst-case scenario, Neso can resort to lowering the grid\u2019s voltage to prevent a widespread blackout or even disconnect large industrial energy users to keep the lights on in homes across the country. \u201cBut that\u2019s what you\u2019re hoping you never have to do. That\u2019s the last thing you want,\u201d they said.<\/p>\n There was a short-lived blackout in the UK in 2019 when a lightning strike caused two electricity generators to disconnect from the grid. Photograph: Yui Mok\/PA<\/p>\n T\u200bhe pressure to avoid reputational damage would be nothing new for those in the Wokingham control room. Neso became a state-controlled body after the government bought it<\/a> from the FTSE 100 energy company National Grid in late 2024 for \u00a3630m.<\/p>\n Under its previous ownership, engineers were aware a misstep could hit National Grid\u2019s share price; now they face the weight of expectation to balance supply and demand without a hiccup as more clean energy sources come on to the grid and Labour pushes to hit a 2030 green energy target<\/a>, the former control room worker said.<\/p>\n \u201cWhether there were direct orders to cover up a scandal or not, individuals are potentially being put in an invidious position that might inhibit them from taking the correct action. There was always that sense of being wary of how your actions might be viewed by those higher up. This might mean not taking timely actions [to rebalance the system] if you are fearful that it might cause senior managers to look askance,\u201d they added.<\/p>\n In a letter to the industry regulator for Great Britain, Ofgem, the Neso chief executive, Fintan Slye, said the system operator had \u201cpolicies and procedures in place\u201d to ensure that this kind of influence could not take place. \u201cNevertheless, we take these allegations extremely seriously\u200b,\u201d he said. A spokesperson said the Eversheds investigation will be shared<\/a> with Ofgem and the government, and ultimately published. It is unclear exactly when that will be.<\/p>\n","protected":false},"excerpt":{"rendered":"In a control room in Wokingham, Berkshire, staff work around the clock, minute by minute, to align Great…\n","protected":false},"author":2,"featured_media":704726,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[59,57,58,50,56,54,55],"class_list":["post-704725","post","type-post","status-publish","format-standard","has-post-thumbnail","category-united-kingdom","tag-gb","tag-great-britain","tag-greatbritain","tag-news","tag-uk","tag-united-kingdom","tag-unitedkingdom"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/704725","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=704725"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/704725\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/704726"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=704725"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=704725"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=704725"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"\"](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2026\/06\/500.jpg\")
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