Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Platform | Frequency (per hour) | Destination | Service Pattern | Operator | Line |
| --- | --- | --- | --- | --- | --- |
| 1.0 | 4.0 | Highbury & Islington | All stations via Shoreditch High Street | London Overground | East London |
| 1.0 | 4.0 | Dalston Junction | All stations via Shoreditch High Street | London Overground | East London |
| 1.0 | 4.0 | London Bridge | All stations | Southern | Metro |
| 2.0 | 4.0 | Crystal Palace | All Stations | London Overground | East London |
| 2.0 | 4.0 | West Croydon | All stations | London Overground | East London |
| 2.0 | 2.0 | London Victoria (Mon-Sat) | All stations via Clapham Junction | Southern | Metro |
| 2.0 | 2.0 | Caterham (Mon-Sat) | All stations via East Croydon | Southern | Metro |
| 2.0 | 2.0 | West Croydon (Peaks & Sun only) | Sydenham then fast to Norwood Junction | Southern | Metro |
Question:
When London Bridge is the destination, what is the frequency?
Answer:
4.0