Tennis fans have been warned that they face being turned away from Wimbledon if they buy invalid tickets over the internet.
According to reports, online auction sites are doing a brisk trade in the prized tickets.
But Wimbledon bosses have warned users that the majority of tickets issued for the tournament are only valid for the original buyer and cannot be resold - although many internet buyers are apparently not told this.
Only tickets that are allocated by Wimbledon under its debenture scheme can be resold and used by any buyer; other tickets can only be used by the original purchasers.
"People have been refused entry because of this," warned a spokesperson for Wimbledon's legal representative.
The tickets become invalidated if anyone else attempts to use them.
Fans are at a huge risk, as the auctions on the internet do not state whether the tickets are debentures or not.
The spokesperson warned that buyers should "make contact with the seller, either in person or over the telephone, until you are sure that they are bona fide".
Fans are desperate to get their hands on tickets. Two tickets for the men's final are being auctioned on eBay for £1400, with the seller claiming he has had 18 bids for the tickets.
Another set of tickets advertised by a seller in Bath have so far reached £902.
The ticketing scare highlights the perils for users of buying goods 'blind' from online auctions.
The eBay site says: "We have no control over the quality, safety or legability of the items advertised, the truth or accuracy of the listings, the ability of sellers to sell items, or the ability of buyers to buy items".
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