Rugby fans have been warned not to buy tickets from touts after police seized a parcel containing 300 tickets for World Cup games.
A 30-year-old man was arrested at property in Essex in connection with an investigation into ticket fraud, the Met said.
The force searched two addresses, one in Essex and one in south London on Wednesday, after discovering a parcel last week containing hundreds of tickets for the tournament.
The man has been bailed pending further enquiries.
Superintendent Jo Edwards, spokeswoman for the policing of the Rugby World Cup, said people keen to attend matches should not risk paying huge sums to touts for tickets which may not get them into games.
She said: "Our advice is simple; do not buy tickets from touts or unauthorised sites. You not only risk paying well over the odds for the ticket but are likely to find you are unable to get into the event.
"And if you think you have become a victim of a Rugby World Cup ticketing fraud report it to Action Fraud."
Stephen Brown, managing director of England Rugby 2015, urged fans not to buy tickets from unofficial websites.
He said: "Tickets are on sale now, at face value so there is no need to risk paying inflated prices or buying from unofficial sources.
"Buy official tickets from tickets.rugbyworldcup.com - the official site which is safe and secure."