Friedrich Kramer of the Cologne police finds the British approach to prostitution unimaginable. In Germany, brothels are legal, sex clubs are tolerated and street prostitution is treated as an offence little worse than parking on a double yellow line. InCologne's bookshops you can buy a map which rates the nightclubs, saunas and brothels according to performance, service and atmosphere.
"Relaxation around the clock" is promised at the Eros Centre in a quiet street just north of the city centre. A notice in six languages warns: "The carrying of drugs or weapons in the establishment is forbidden. Offenders will be handed over to the police."
A DM5 entrance fee (£2) allows the customer through the turnstile into the low-lit lobby-cum-bar. A couple of dozen women sit chatting, waiting for customers.
Two hundred women work in the upstairs rooms. In the words of 38-year-old Jochen G, one of the managers: "We work together with the police - and we have a good relationship. We're like a safety valve for society."
The women pay the management £100 a day, of which the taxman takes a slice. Condoms and regular health checks are compulsory. On the manager's desk lies a sheaf of slips from the local health authority, giving the women the all-clear. Once prostitutes
have paid their fees, their takings are their own. "We're like a normal business," says Mr G.
The prostitutes are evangelical in their support for this system. The visiting journalist is quickly surrounded by curious women keen to get their points across.
Barbados-born Michelle says: "When I'm in England I feel frightened even if I break down on a motorway. Here I'm safe.''
Michelle and her colleagues are the lucky ones. Prostitutes in clubs and saunas, including many from eastern Europe, tend to be less protected.
Few argue that prostitution itself should be illegal. One result of the consensus is that street prostitution - officially banned in many districts of Cologne - is almost invisible.
Police say there are around 300 street prostitutes in Cologne out of a total of 6,000. "They tend to be the drug addicts," says Mr Kramer. "Usually, they get a warning."
Even in the partly residential district just north of the main station, best known for its illegal street trade, there is little indignation.
Cilli Rosewick, a 70-year-old retired book-keeper, says: "I have lived here for 30 years. Occasionally the men used to bother me. But the customers were not usually a problem."
She is surprised that anyone might object to brothels. "Is that illegal in England?" She shakes her head in disbelief.