A £50,000 investment for 10% equity represents a 10% ownership stake in the company.
Equity is the ownership percentage offered to an investor in exchange for money or other agreed value. In this example, the entrepreneur keeps the remaining 90% before considering any other shareholders or later changes to the company structure.
The implied valuation is £500,000 because £50,000 is one tenth of £500,000. That calculation is why equity negotiations are central to Dragon's Den: the cash amount and the percentage together show what valuation the entrepreneur is proposing.
An offer on television is not automatically a completed investment. Due diligence and legal negotiations take place after filming, and an agreement may change or fail to complete.