Most EU, US, Canadian, Australian, Japanese and other visa-waiver nationals may visit the UK without a visa for business meetings, trade shows and conferences up to 6 months, but must hold a UK Electronic Travel Authorisation (ETA, GBP 16 / approx. USD 20) before boarding — apply online in advance. Nationals without a visa-waiver agreement need a Standard Visitor visa (GBP 127 / approx. USD 160), which can be applied for up to 3 months before travel and is usually decided in around 3 weeks. Carry a printed invitation or registration confirmation from the organiser for the border, and confirm your own nationality's rules on gov.uk before booking.
Estimated cost: Varies by visa type and nationality (check official site).
Processing: Varies by nationality; apply several weeks before travel.
Not a visa — a pre-travel permission. Required for visa-waiver nationalities; check gov.uk for the current eligible nationalities list. Carry your organiser invitation or registration confirmation and proof of accommodation for the border interview. Fees are published government fees and are reviewed periodically.
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