A financial service organisation wants to foster a risk-taking culture. Which strategy best supports this goal?

The correct option is:

• Encourage employees to experiment and learn from failures while managing risks.

This strategy best supports fostering a risk-taking culture because it promotes active engagement in new ideas and initiatives (experimentation) while acknowledging that failures are part of the learning process. The phrase "while managing risks" indicates a balanced approach, where risks are taken but not recklessly, which is crucial for a financial service organization.

The other options are less suitable:

• Launching initiatives without assessing risks is irresponsible.
• Minimizing all risks by waiting for proven ideas is the opposite of a risk-taking culture.
• Only allowing senior executives to take risks does not foster a widespread risk-taking culture among all employees.

The final answer is $\boxed{\text{Encourage employees to experiment and learn from failures while managing risks.}}$