Some people already know that something must be very wrong.There is a standard field kit: low-lux cameras that take pictures when there is very little light, long-range lenses, binoculars and hidden cameras. Most of our work is done with digital cameras: video film is not used at all any more. Though a client can bug their own phone, only someone very foolish would be making calls off their own landline. Or those who say they are bachelors, who turn out to have a family or long-term girlfriend who is unaware they are on the dating scene.

So often both people are slightly suspicious.We treat every case individually and are going into the unknown every time the phone rings. It is not just married people who contact us – there are people who have been going out with each other, maybe for four months, and they have never been round to their boyfriend or girlfriend’s house. They are starting to ask questions, and want to find out about that person’s background. This can happen when a single mother with children is in a relationship, and they want to check who the person is that is spending time with their children. There are cases where people think they are going out with a Special Forces commando and we find out they actually deliver pizza. For some, just catching someone somewhere they shouldn’t be is enough.

For others, it’s simply catching someone with someone they shouldn’t be with. Lots of people do not even need to see the surveillance footage, but will just read the log notes But there are some people who want a lot more. The most you tend to get is people holding hands when walking down the street or having a snog. Large parts of affairs take place behind closed doors.We do get some repeat customers, who may come back two or three times over a decade.

They may want us to do background checks on new partners, or on the same partner several years on, particularly if they have forgiven them for having an affair once. These individuals tend to be very wealthy, or very mistrusting. Some of the most insecure people are people who cheat on their partners themselves. If you are capable of having an affair, you may believe that everyone else shares that capability.There are a lot of female operatives nowadays, and in many situations people are less suspicious of a woman than a man.

If somebody’s having an affair, they are often seeing somebody who themselves has a partner. We followed him on to the plane to America, by car into Canada, but again, the most dramatic thing he did was to drink a few beers in a bar.Different clients require a different degree of closure. But it is amazing how many people having a clandestine meeting in a restaurant choose to sit in a window seat because it is more romantic. At which point it is not difficult for us to film from outside. If we see a client’s partner going into a restaurant we’ll try to send in an operative to sit on the adjacent table. It’s harder to explain away holding hands than kissing, which can be platonic.Things are not always what they seem.