Place the tomatoes, garlic, olive oil, bread, cream, sherry vinegar and salt in a food processor. Blend until smooth. Pass through a sieve into a clean bowl. Transfer back to a clean food processor and keep the motor running as you drizzle in the chilled water in a slow steady stream. Cover and chill until ready to serve.
When ready to serve, grill the bacon under a hot grill for 4-5 minutes, turning occasionally, then remove and drain on kitchen paper. Ladle the soup into serving bowls and garnish with the bacon.