How do I write a speculative cover letter when there is no job advert?

Be specific about what you want, what you offer and why this employer, then ask for a small, easy next step. Without an advert, the reader has no reason to read on unless you make one quickly.

Structure:

• Opening: who you are and the type of role you are interested in.
• Why them: one specific reason based on research, such as a new project, expansion or their service area.
• Why you: one or two achievements relevant to that team.
• Ask: a short call or keeping your CV on file.

Example opening: "I am a qualified electrical engineer with five years in commercial fit-outs, and I am writing to ask whether your MEP team in Abu Dhabi expects to recruit site engineers this year."

Keep it under about 250 words. Send it to a named person and follow up once after a week or two if you hear nothing.