When you invest £X in a scheme, and then quickly turn around and claim a loss of up to five times £X you likely stray to the wrong side of the avoidance/ evasion line.
The ruling in this case is the schemes were not genuine investments, and so any claim for losses incurred against tax liabilities were not valid under HMRC rules attached to these reliefs. So not quite as serious as serious as deliberate tax evasion, but they will likely have to pay back the reliefs they received.
They invested £5.2M (getting full tax relief on that), then topped up their investment with a £20.8M offshore loan. A month later, their investment reported a £25 loss, which they then wrote off against their tax liabilities.