British cybersecurity company Arqit Quantum is facing an investigation from the US Securities and Exchange Commission over its merger with a special-purpose acquisition company last year, the company disclosed on 14 December.

Arqit saw its market value rise from $1.4bn to over $4.5bn soon after it completed the Spac merger — a form of public listing — in September 2021 as investors embraced the company and its projections of surging revenue and profits in the emerging sectors of digital security and advanced cryptography. Its shares have since fallen significantly amid a broad investor retreat from Spacs and young high-growth companies.