For transactions to which the Takeover Code (www.practicallaw.com/0-107-7362) applies, matching rights given by a target are generally prohibited under Rule 21.2 of the Takeover Code. In the context of recommended bids (www.practicallaw.com/0-107-7116), a matching right, under which the target board agreed not to withdraw its recommendation of the bidder's offer if it received a higher competing offer, without first allowing the bidder the opportunity of matching the competing offer within an agreed time period, was a deal protection measure which was in frequent use before the general prohibition on offer-related arrangements was introduced into the Takeover Code on 19 September 2011. (If the bidder matched the competing offer, the target board was obliged to continue to recommend the bidder's offer.)
For examples of takeover offers where there was a matching right, see What's Market, Public M&A deals: matching or bettering right.