"1. .... Subject to you being medically fit for service abroad, (and your family being medically fit to accompany you), I am now able to formally offer you the post of Garrison Youth Worker Herford in the Federal Republic of Germany for a period of three years commencing2 July 1990 .
"4. Your offer of appointment is for employment in one particular country in the area abroad concerned and while you will not normally be moved from one area to another you may be moved to any establishment within the administration of that area."
"11. In general, however, your appointment will be governed by regulations applicable to Ministry of Defence UK based non-industrial civilians serving abroad."
"offer of appointment as a UK based Youth Worker under the terms and conditions set out in our letter of18 May 1990 ."
"These troops are accompanied by their families, and by a civilian support element, and together comprise a substantial British population, mainly in Northern Germany. .... ."
"will not normally be moved from one area to another"
"8 .... if, under his contract, the employee can only be required to work in Germany it must be a contract under which he ordinarily works in Germany [and therefore outside Great Britain]. Indicators of a headquarters elsewhere, to the location of which much of the administration of the contract is assigned, cannot alter that fact."
"If the contract by its express or implied terms requires that the employee should do his contractual work wholly, or substantially wholly, in Great Britain, the answer will normally be simple. So, conversely, if under the contract the contractual work has to be carried out wholly or substantially wholly outside Great Britain. This will dispose, quite simply, of many cases."
"5. The Respondent [Mr Capel] was engaged by ..... letter of employment dated18 May 1990 .... . The letter stated that the post offered was in the Federal Republic of Germany ... ."