If you are conducting perfectly legal employment and have found yourself being threatened, you are just as entitled to the protection of the authorities as anybody else. Unfortunately many Pl's do not take this option as they do not wish to draw attention to themselves. I can understand this, but in general I would advise that at least having this as an option would be a sensible precaution and in some cases it should be the primary option under consideration.

If you are involved in a serious commercial investigation involving illegal dealings, smuggling, embargo­ busting or whatever, you will be far better off involving the authorities as soon as you recognise the  threat to yourself. Their resources are first-class and their intelligence is second to none. You must con­sider the threat to yourself above the needs of your client as it his not his neck on the line.

If, while driving, you are subjected to an attack of some form, such as being "nudged" from behind, drive immediately to the nearest Police Station and do not be afraid to enter the car park despite any notices to the contrary. It is bound to be under the watch of surveillance cameras and so your pursuers are un­likely to follow you in. It may be an attempt at mugging rather than anything more serious and you can always give this as a reason for your actions. Only if  the Police require further information should you offer details  of what  you  are involved in.

Having reported their details and notified your client, you should seriously consider whether you wish to continue this contract, or even if you need to! Consider your personal safety before taking the risk of continuing - especially as you are aware of just how seriously they take your activities. If you are re­quested to continue in order to gather further proof and to assist the authorities in catching these pur­suers then do so with your eyes open. Be aware that you are unlikely to be covered by insurance , either personally or for your vehicle, and that you have a risk to yourself that may well extend beyond any monetary  incentive that  is being offered.